ISSN 0968-0446 _~ Bulletin of The Natural History Museum Botany Series S)2 NATURAL HISTORY MUSEUM VOLUME 25 NUMBER 1 29 JUNE 1995 The Bulletin of The Natural History Museum (formerly: Bulletin of the British Museum (Natural History)), instituted in 1949, is issued in four scientific series, Botany, Entomology, Geology (incorporating Mineralogy) and Zoology. The Botany Series is edited in the Museum’s Department of Botany Keeper of Botany: Dr S. Blackmore Editor of Bulletin: Ms M.J. Short Papers in the Bulletin are primarily the results of research carried out on the unique and ever- growing collections of the Museum, both by the scientific staff and by specialists from elsewhere who make use of the Museum’s resources. Many of the papers are works of reference that will remain indispensable for years to come. All papers submitted for publication are subjected to external peer review for acceptance. 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(Bot.) 25(1): 1-93 Issued 29 June 1995 A revision of Rutilaria Greville (Bacillariophyta) ROBERT ROSS The Garden House, Evesbatch, Bishop’s Frome, Worcester, WR6 5BD CONTENTS MAELO MUCHO eee eee ee ITE Mate eee cae tc ee ais asin ew adatn pene hidceeeiceebie be da fawetnn tae aisle dellsio Jong debs islets siddia'le ol 2 ULC ESCM SPE CLIIGHSM Az J-cect cesarean aad. eeC eee SUIIIUR.,... «aay doe dame ette diane = tele Weide sosaaciderlniet neds necytaclens 3 FRAKOTIGHIIC ACEOUE ISIIes se aeen esses acta e ae eee aa ale owns» enh tmebdnm: Sues doneegeencnck ostiscemeinccotpbampsansanunsmans +See. 9 IDI ARTCC VIN Nata se te creas nae ee eee ee RRP SCER ED oe sion npc Goan cman eB ecin ans ancinedqans oc ashEiaiis~ nlbceces cases > stivccepeingea tame SOL aOk er Pecele, He a bets Maoist 5. BA oes ae Se 48 DA alee PRD PLAT UTITI OLE CT Gtr LOVE! camctua tease etc c Sessa sic Be PA dts Blah ee btlte ey cae aeaele Mes SRUBU MEER suis shiecetanc cataaees 49 DSO Me LCMUBIA IR MEROSS cede coeatesetteee notices sae te ctles fe ois.s ssiers Salada aah cheetohice w dae Rem ete « alttaaRie a teseslcte ei oblaaislelte vseieiisines 51 POMC S ZUNGICLISISHL ANUOGS eRe Meet ene Metta erento Pet anos oc deiaciicn cise Chas ciopisiaa or et des iteS» Seplabraasts (ats bee srcsa menietist 52 ZR RMED SOM GLEVULC™ eeetease sacs Matter ete oet sates tes oc vas Gretate Ta cumioiyates adlaachl owicitsipsoaiieiielivn «ep wacgdh «sstiidelee sve stebile ass 54 DERN ODESAAGT COMICS CIE Ver siete one eee a eee «os ons cemaaieiians ostaphirc smamanieg oceaeamsaneespine ncaa sins sary des sdeeseinenels 58 TASUMfiCLENtLYAMOWOUSPEGRES eee ats aise es cele ee en ae «ec oo siguientes salen ae Soa cen a ec giersed seis cieicois el cies nines ec siisie ne 63 SPE CLES SMEG CHIC Lema Pee eee ste eet elem a AM tates os iso. capins ciainlentta siete nile in esiinnenalicleiniine'o Swtbijele ws nleipiinlinin sinc cn 64 TIS CHISSIO mbes sha Mee see erste tater aite Nan ae lec Aaa: oOo ais os nan alindige vccincanaeanmadingebisiintbnin sianincneeeinsesinine ais seasieassenes seine 64 FRELS MERC SM Peper ary een ere SPB re a EER oo oes Beeinntv deere nintendo nindniae n seibieiss Zeinnidlesivies dssie'ecjos snwis Gaiseasisadiales 91 Synopsis. Detailed descriptions of Rutilaria Greville and its species and subspecies are given, based on light microscopy and, for most taxa, on scanning electron microscopy. Rutilaria is characterized by the presence of a periplekton in the centre of each valve; this is a rimoportula with an external part consisting of a tubular stem from © The Natural History Museum, 1995 R. ROSS the top of which two arms arise and encircle the stem of the periplekton of the sibling valve. Syndetocystis Greville and Syndetoneis Grunow are shown to be synonyms of Rutilaria. There are 28 species, five of which are divided into two subspecies. Thirteen new species and all five non-type subspecies are described as new, and two new combinations are published for the species hitherto placed in Syndetocystis and Syndetoneis. Only two species are found living, and both of these have fossil records. Six others are recorded with certainty from the Neogene, and the one sample in which another is found may be Neogene or Paleogene. Only one of the species with a certain Neogene record is not also known from the Paleogene. The living species are members of the neritic plankton and this is the probable habitat of most, perhaps all, of the fossil ones. The Rutilariaceae are a monotypic family, probably derived from the Hemiaulaceae and probably:ancestral to the Cymatosiraceae. INTRODUCTION Diatoms of many genera, both recent and fossil, have their frustules united in inseparable chains. In almost all cases the structures that hold pairs of sibling valves together are spines modified to a greater or lesser extent, i.e. they are structures projecting from the frustule that are solid or, if hollow, closed. In Rutilaria Greville, however, there is in the centre of each valve a modified rimoportula that interlocks with that of the sibling valve. This is called the periplekton, a term proposed by Jurilj (1965), whose description of the structure was, however, very inaccurate. Externally the periplekton consists of a vertical hollow tube from the top of which two arms arise that encircle the vertical tube of the periplekton of the sibling valve. This can be seen by careful observation with the light microscope. Nevertheless, the first accurate descrip- tion of the periplekton was that of Ross & Sims (1972), which was based on scanning electron microscopy. That the peri- plekton is a rimoportula with its internal opening a straight slit across a slightly raised papilla can only be seen by scanning electron microscopy. One can see with the light microscope that the monotypic genera Syndetocystis Ralfs ex Greville and Syndetoneis Grunow also have a periplekton with the same structure externally as that of Rutilaria, and this has been confirmed by scanning electron microscopy (see Plate I (b), (c), (e), (f) and Plate III (c) and (d)). This is by no means obvious from the published accounts and illustrations, which are either too inaccurate or too incomplete. All species of Rutilaria, Syndetocystis and Syndetoneis are bipolar and bear at each pole an ocellus (see, e.g., Plate I (b), (f), Plate V (d), Plate VI (c), Plate XIX (d)). Although these are readily visible with the light microscope, the first mention of them was by Simonsen (1972), who reported their presence on the basis of information that I had given him. It was, of course, not until it became possible to examine diatoms with the scanning electron microscope that it could be seen that the structure at the poles of these genera is a plate penetrated by porelli and thus similar to those of such genera as Auliscus Ehrenb. and Eupodiscus J.W.Bailey, although without the thickened surrounding ring present in them. It was rather more than forty years ago that these facts came to my notice. Amongst specimens from the upper Eocene deposit at Oamaru, New Zealand, that I was identify- ing was one of Syndetocystis grevilleanus Walker & Chase, the earliest name for the type species of Syndetocystis. When I realized that this specimen might belong to that species, I examined both the original material and the published descriptions and figures. This showed that the only accurate and comprehensive description that had been published by then was that in the protologue of the generic name (Greville, 1866), which did not include an illustration. All the subse- quent descriptions and figures under various specific names were either inaccurate or incomplete. Examination at the same time of specimens of Syndetoneis amplectans (Grove & Sturt) Grunow and Rutilaria radiata Grove & Sturt, both present in the same fossil material, showed that none of the characters that distinguished these two species from one another and from Syndetocystis were a sufficient basis for generic separation. They differed only in: height of the vertical tube of the periplekton and the shape of its arms; height of the elevations at the poles; arrangement and size of the areolae; situation of spines. Examination of other species of Rutilaria showed that all of them had an ocellus at each pole and a periplekton of similar structure. The two arms of the periplekton are equal in Syndetocystis grevilleanus, Syndetoneis amplectans and Ruti- laria radiata, but in many of the other species of Rutilaria the two arms are dissimilar, one being longer than the other and differently shaped (cf. Plate III (d), Plate XII (b), Plate XIX (b), Plate XX (d)). This difference, like those listed above, is an insufficient basis for separation at generic level, and it is clear that all the species with a periplekton belong to a single genus. No detailed accurate description of this genus has been published, the nearest approach to this being the account of Rutilaria provided by Round, Crawford & Mann (1990), who also give a description of Syndetoneis amplectans under the name Syndetocystis. In some species of Rutilaria the diminution in size of the valve with successive vegetative divisions is accompanied by very considerable changes in outline, greater than those in any other genus. The largest valves have an elliptical or sub-hexagonal central portion and capitate or subcapitate projections each twice as long as the central portion or even longer; the smallest valves are without projections and are similar in shape to the central portion of the larger ones (see Figs 19, 76). Whilst there is thus great difference in length between the largest and the smallest valves, the difference in width is small. As a consequence of this wide range in the outline of the valves, more than one name has been and is still applied to these species. This, and the existence of a number of undescribed species, made the need for a taxonomic revision obvious. It was also a necessary preliminary to establishing which, if any, of the species might be useful in stratigraphy. The great increase in our knowledge of the morphology of diatoms resulting from the use of the electron micro- scope has shown the inadequacy of the system of classifica- tion previously accepted for them. A number of suggested revisions have been put forward (Simonsen, 1979; Glezer et al., 1988; Round, Crawford & Mann, 1990), but they differ very considerably and no consensus has yet emerged. REVISION OF RUTILARIA GREVILLE (BACILLARIOPHYTA) The relationships of Rutilaria are far from obvious and need to be examined in the light of a detailed and accurate account of its morphology. There are thus many reasons why a monograph of the genus is required, and it is hoped that this account, started long ago and now completed after many interruptions, will go some way to meeting those needs. It is, however, to some extent at least, an interim account rather than a final one. There are illustrations in the literature of specimens that appear to belong to three different species of which I have not myself seen specimens (see pp. 63-64). This is, however, not the main reason for considering this as an interim account. Rutilaria is primarily a fossil genus; only two of its twenty- eight species are known living and both of these have fossil records. In all the fossil deposits from which the genus is known it is rare or infrequent. Few fossil deposits have been studied in such detail that we have an adequate knowledge of their floristic content. Although fossil deposits exposed on land have been studied for more than a century, there has until recently been a strong bias against detecting the smaller species present. These were discarded when samples were being prepared in such a way as to provide specimens not even partially obscured by broken fragments, e.g. when samples were sieved. It is only in recent years that this has not been normal practice. In spite of the comparatively intensive study of the Paleocene and Eocene deposits of the Volga basin in Russia during the late nineteenth and early twentieth centuries, the presence of small species of Rutilaria in these was not known until their discovery by Anisimova was reported (Proshkina-Lavrenko et al., 1949). Dr F. Hustedt later retained the small specimens when preparing material of Paleocene age from Inza, Ulyanovsk oblast, Russia. In this material there are four small species of Rutilaria, described below as R. minima R. Ross, R. delicatula R. Ross, R. hyalina R. Ross and R. hustedtii R. Ross. Three of these species are no doubt those recognized by Anisimova, but all of them were otherwise previously unknown. The fossil diatomite of late Eocene to early Oligocene age from Oamaru, New Zealand, has been even more compre- hensively studied than the deposits from the Volga basin. Nevertheless, a small species of Rutilaria, R. areolata Sheshukova-Poretskaya, is first reported from Oamaru in this monograph. Specimens of each of the two subspecies of this species are present on microscope slides, now in BM, pre- pared by H.-J. Schrader when studying the pennate diatoms of the Oamaru diatomite (Schrader, 1969). Because of the small size of many pennate diatoms, he had not discarded the small specimens in the samples that he studied. The study of diatom biostratigraphy began about thirty years ago at the time when core samples from the ocean floor began to be available. Since then, the smaller diatoms have not been discarded. Nevertheless, specimens of Rutilaria present in samples examined in these studies are likely to have gone undetected. Biostratigraphers are primarily inter- ested in those species that are frequent in the material that they are studying. Accordingly, they normally examine only two or three strewn slides from each sample, and often ignore the species that are rare on these. Rutilaria, however, is infrequent or rare in all the fossil samples in which it has been found and, although present in the material studied, might well not occur in the portion examined. The results of a study undertaken by Doig (reported in Edwards, 1991) show this. In order to compare the diatom assemblages in 40 different outcrops of the Oamaru diatomite, he identified and counted 3 300-500 specimens from each outcrop, 14 980 specimens in all. Amongst these less than 100 of the over 600 species known to occur in the Oamaru diatomite were represented, and there were only two specimens of Rutilaria, both of the same species identified by him as Syndetoneis amplectans. In this monograph there are records of nine species of the genus from the Oamaru diatomite. Rutilaria is a neritic genus, and fossil deposits of diatoms laid down in shallow water are much more diverse floristically than those from deep sea localities. To find specimens of the genus in fossil deposits laid down in shallow water, whether ones already available but not intensively studied or ones newly discovered, will require prolonged searching. If this is done, it will undoubtedly extend our knowledge of the geographical distribution and the range in age of the species of Rutilaria already known and will also reveal the existence of others not yet described. SOURCES OF SPECIMENS In the course of preparing this monograph specimens from the localities listed below have been examined. They are arranged in a rather irregular sequence from west to east, beginning in western Europe. Most of the sources of material are fossil deposits and their age is given as precisely as the available information allows. Whilst the provenance of samples collected in the recent past is usually known exactly, the amount of detail available for some of those collected longer ago is often less adequate. In particular, there is often doubt about their precise geological age. Where this is so, the range of ages within which they might have been deposited is indicated in the form ‘middle Eocene—Oligocene’. When the sample from which a specimen comes is known to date from very close to the boundary between one period and another but there is doubt about which side of that boundary it comes from, the age is given as, e.g., ‘late Eocene to early Oli- gocene’. A number of the locality records given in the taxonomic account are based solely on the literature. For the most part all the information about the provenance of the specimens on which they are based is contained in the publication cited; where additional information is available it is given below. Portugal Redondo, Alto Alentejo Province There is a strewn slide (BM coll. Adams J5185) labelled as from this locality. It came from the collection of F.B. Taylor and had been sold by Messrs C. Baker of London. Taylor (1929: 158) includes this locality in his list of the ‘most interesting localities’ for diatoms, but there is no other record of diatoms from there. The floristic composition is very similar to that of the upper Miocene material from Malaga Cove, Los Angeles County, California, U.S.A., often said to be from Redondo Beach or San Redondo, Los Angeles County, California, U.S.A. (see p. 7 below). It is thus highly likely that “Redondo, Alentejo’ on the label of this slide is an error for the Californian locality. 4 France St. Laurent-la-Vernéde, Gard Details of the fossil deposit at this locality are given by Lefébure (1935) and Monjanel (1987), who dates it as early Miocene. Denmark Knudeklint, Island of Fur Specimens of Rutilaria were found in portions of samples D 292 and D 294 from this locality kindly sent me by Dr M. Homann. These samples come from near the Paleocene to Eocene boundary. For details see Homann (1991). Slovakia Pétor (Szent Péter), Banska Bystrica region According to Hajés (1986: 162, 165), this deposit is lower middle Miocene, as also is the deposit from Velky Krtis (Nagykurtés) from which Pantocsek (1889) records Rutilaria philippinarum and R. szakalensis. Hungary ‘Castel’, Szurdokptispoki Cheneviére distributed fossil material labelled as coming from ‘Castel’. The diatom flora that it contains shows that it is the material which is the subject of Cheneviére’s (1933, 1934a) account of diatoms from ‘un dépdt nouvellement découvert pres de Szurdokptisp6ki, au voisinage du chateau’, a deposit that he dated as late Miocene. This dating is, however, open to question. Holmes & Brigger (1979) give in translation an extract from a letter from Cheneviére to Brigger written in 1938 in which he says of this material: ‘this earth is very difficult to obtain; the outcrop is no greater than 1 m’!! and it is the only marine part in the middle of a very large freshwater deposit; its presence is incomprehensible.’ This indicates that this marine diatomaceous earth is a block of older material that is not in situ but had become detached, transported into a body of fresh water and incorporated into the sediments forming there. If this is the case, it is older than the freshwater deposit in which it occurs. According to Hajos (1986: 169-171) this is of middle Miocene (Badenian) age. One cannot tell how much older the ‘Castel’ marine material is, but its floristic content indicates that it is Neogene rather than Paleogene. Marine diatomaceous deposits from the lower Miocene and from earlier in the middle Miocene are known from a number of localities some 50 km north of Szurdokptsp6oki (Haj6s, 1986), i.e. from higher in the valley of the river GyOngy6s, and this area would seem to be the most likely source of the ‘Castel’ material. Its diatom flora does, however, include a number of species that have not been found in any other locality. There can thus be no certainty about either where it came from or its precise age. It cannot, however, be younger than the middle Miocene, and specimens from it are listed as being of that age, although they may be older. R. ROSS Szurdokptispoki There is a specimen of Rutilaria in CAS which came from material collected by Hajos in 1960 which is labelled as coming from Szurdokpiispoki and as being of Tortonian, i.e. late Miocene, age. This presumably came from the upper marine diatomaceous beds exposed in the diatomite quarry at Szurdokpiispoki, which Hajdés (1986: 171) now dates as Badenian, i.e. middle Miocene. Nogradszakal According to Hajos (1986: 179-182), the deposit at Nograd- szakal (Szakal of Pantocsek, 1886, 1889) is late middle Miocene in age. Ukraine Dneiper — Dombas depression A micrograph of a specimen with the information that it came from late Eocene material from this area was sent me by Dr A. Ol’shtynskaya. Russia Kantemirovka, Voronezh oblast Photomicrographs of a specimen of Rutilaria grevilleana from the late Eocene deposit at this locality were sent me by Dr Strel’nikova. She misidentified this as R. limoniformis (Strel’nikova, 1987). Voronezh anticline, Voronezh oblast A micrograph of a specimen from the late Eocene of this area was sent me by Dr A. Ol’shtynskaya. Sengilei, Ulyanovsk oblast Probably early Eocene but possibly Paleocene (see Ross & Sims, 1985: 280). Inza, Ulyanovsk oblast Paleocene (see Glezer in Glezer et al., 1974: 110) Kuznetsk, Penza oblast According to Glezer (in Glezer et al., 1974: 135), the fossil material from this locality studied by Pantocsek and other late nineteenth and early twentieth century diatomists is late Eocene in age. However, according to Dr J.A. Barron (in litt., 1994), the late Eocene dates assigned to some deposits by Russian diatomists were based on incorrect information about the age of formations in California and Barbados and the deposits in question are older. He kindly examined a sample of the classic fossil material from Kuznetsk and found that it was from the early middle Eocene. REVISION OF RUTILARIA GREVILLE (BACILLARIOPHYTA) ‘Kamischev’, presumed to be Kamyshlov, Sverdlovsk oblast Cheneviére (19345) gave an account of the diatoms of a fossil deposit that came, he said, from ‘Kamischevy’, and he distrib- uted material of this deposit. However, the actual locality from which it came is uncertain. Both Glezer (in Glezer et al., 1974: 136) and I (Ross, 1972) independently came to the conclusion that it came from Kamyshlov in Sverdlovsk oblast. Both Jousé (1955) and Glezer date the material from there as late Eocene. However, Dr Barron kindly examined a sample of the material distributed by Cheneviére and reported (in litt., 1994) that its age is early Eocene. This too appears to be the age of Jousé’s material from Kamyshlov, and it seems reasonable to assume that the deposit from Irbit studied by Krotov and Shibkova (1959) is also early Eocene. Til’ tim, Tyumen’sk oblast Campanian, late Cretaceous. Exposure XI/14, sample 14, for which see Strel’nikova (1974), is the sample indicated, prob- ably erroneously (see p. 000) as the source of a specimen of Rutilaria. Coast of Arabia Recent material not more precisely localized. Tanzania Zanzibar Recent material. Indian Ocean Mascarene Ridge, 10° 25'S, 63° 15'E, 3115 m depth, dredge sample. Dodo-123-D1 This sample is from the boundary between the middle and the upper Eocene (see Holmes & Brigger, 1979). Ninety East Ridge, 11° 20.21'S, 88° 43.08'E, 1655 m depth. Deep Sea Drilling Project Hole 214, core 38, section 2, 100-102 cm. This sample is from the Paleocene (see Shipboard Scientific Party, 1974). Indonesia, Java Goenong Gamping, near Nanggoelang, sample AY-12 This sample is from the middle Miocene (see Reinhold, 1937: 57, 58). Road from Mantoep to Pelang, Station 109M, Java Kaarteering-Sheet 109D (Lamongan) no. 83 This sample is from the East Java Horizon, Poetjangan layer, which is late Pliocene in age (see Reinhold, 1937: 57, 59, 67). North side of mountain near Boetak. sample BS-8, Pithecanthropus skull sample of Prof. Dubois This sample is from the middle Pleistocene (see Oakley et al., 1975: 113-114). Indonesia, Makassar Strait Recent material. Indonesia, Sulawesi Recent material. Philippine Islands Recent material not more precisely localized. Jolo, Sulu Archipelago Recent material. Mindoro Strait Recent material. Manila Recent material. Chinese canned fish For the provenance of this recent material see Fuge (1937). Japan Specimens with a locality no more precise than this were all mounted in the nineteenth century. They may be Miocene or early Pliocene in age. Japan, Honshu Tokyo-wan The material from this locality studied by Brun & Tempére (1889) consisted of pebbles dredged from the sea bed. This material is Miocene but its age within that epoch and the locality of the outcrop from which it came are unknown. Sendai, Miyagi Prefecture Brun & Tempére (1889) say of the sample from this locality: ‘Ce calcaire ... constitue des cailloux roulés de grosseurs trés variables.” This material was thus not in situ when it was collected and the locality of the outcrop from which it came is unknown. Akiba (1987) showed that it is late Miocene in age. Ajigasawa, Aomori Prefecture The details of the sample from this locality are: Maido formation, near Ajigasawa station, Ajigasawa, Maido-mura, Nishi-tsugaru-gun, Aomori Prefecture, Japan, coll. T. Kanaya, 1948. According to Akiba (in litt., 1991) the Maido formation extends from the upper Miocene into the Pliocene. 6 Sado-shima Island Two specimens of Rutilaria come from this island, with no more precise information about the locality from which they came. The most probable source is the Sawane deposit at 37° 59’ 40"N, 138° 15’ 50"E (cf. Okuno, 1952). According to Akiba (in litt., 1991), this material probably comes from the Nakayama formation, which ranges from the late Miocene to the very early Pliocene (see Akiba, 1987). Japan, Hokkaido Specimens from this island not more precisely localized, including those labelled ‘North Japan’, come from one or other of the Miocene or early Pliocene diatomite deposits that occur there. Hakodate, Oshima Miocene or early Pliocene, but no more precise details are available. Netanai, Oshima The material so labelled is presumably from the Neogene Shirikishinai deposit that outcrops at Netanai (see Okuno, 1952). It is probably Miocene. Setana, Miyama Probably from the Kuromatsunai formation that extends from the upper Miocene to the lower Pliocene (Akiba in litt., 1991). The specimens of Rutilaria from this locality do not come from the freshwater deposit mentioned by Okuno (£952: 5); Abashiri, Abashiri There are both Miocene and Pliocene deposits at this locality. According to Kanaya (1959), the material from here is probably early Pliocene in age, but Akiba (in litt., 1991) thinks the flora recorded from there indicates that the classic ‘Abashiri deposit’ is middle Miocene, and this age is accepted here. Tokoro, Abashiri Akiba (in litt., 1991) says that an upper Miocene deposit containing diatoms occurs at this locality. Embetsu, Rumoi (‘Wembets’ of Tempére & Peragallo, 1893, 1912) According to Okuno (1952), this deposit is early Pliocene, but Akiba (in litt., 1991) says that there are both late Miocene and Pliocene deposits at this locality. Teshio, Rumoi (‘Thesiogori’ and “Theshiogori’ of Pantocsek, 1892, 1905) Akiba (in litt., 1991) says that there are both late Miocene and Pliocene deposits at this locality. R. ROSS Bering Sea Komandorsky Islands, Russia The fossil deposits from these islands have been studied by Gladenkov (1991). Their ages range from early Oligocene to late Oligocene. The records from this locality are based on photomicrographs and samples that he kindly sent me. Aleutian Basin, 54° 47' 20"N, 179° 08’ 00”W, 1670 m depth. U.S.S. Albatross Station 4029H Hanna (1929) showed that this sample is as old at least as the middle Miocene. Kisseleviella carina is moderately frequent in this material. This suggests that it comes from the lower Miocene or the lower part of the middle Miocene (see Akiba, 1985, and Akiba & Yanagisawa, 1985). Specimens from this locality are therefore listed as having an early Miocene age. Navarin Basin, 56° 12.3'N, 171° 42.2'W, 2500-2700 m depth. U.S. Geological Survey Research Vessel S.P. Lee, cruise L5-78-BS, dredge sample 2-4 This sample is from the upper Oligocene (Baldauf & Barron, 1987). U.S.A., Oregon Coos Bay, Coos County. California Academy of Sciences sample 1612 This sample is from the upper Eocene Bassendorf Shale exposed at the south end of Coos Bay. U.S.A., California Specimens with no more precise locality are from gatherings made in the nineteenth century and come from one or other of the middle Miocene to lower Pliocene diatomite deposits exposed in the coastal region of California from San Fran- cisco southwards. Antioch, Contra Costa County The details of the sample from here are: Contra Costa County, NE 1/4, Sec. 2, T.1N., R.1E, M.D.M. 21/2 miles S of Antioch. The geographical co-ordinates of this locality are 121° 49’ 49"W, 37° 57’ 48’N. Its diatom flora was described by Hanna (1931), who regarded it as coming from the Kreyen- hagen Shale of late Eocene age (Jenkins, 1931). It is the type locality of the ‘Sydney’ shale of Clark & Campbell (1942); see also Kanaya (1957) and Mandra (1968). According to McLean & Barron (1988) this is late middle Eocene, being in Barron’s informal Triceratium inconspicuum var. trilobatum partial range zone. Laguna Seca Creek, Merced County From 14 miles south of Los Banos at abandoned mine, from cuts near top of section near abandoned process plant, Kreyenhagen shale. This is the Oro Loma locality of McLean & Barron (1988), also in the late middle Eocene Triceratium inconspicuum var. trilobatum partial range zone. REVISION OF RUTILARIA GREVILLE (BACILLARIOPHYTA) Panoche Road, Panoche Hills, Fresno County Mined earth from the upper Eocene Kreyenhagen Shale. Cantua Creek, Fresno County The details of the sample from this locality are: 1/4 sec. 28, T17S R14E, 200-300 feet below top of Lillis Shale. The age of the material is thus late Eocene (see Jenkins, 1931). Salinas, Monterey County Upper Miocene. Diatomaceous material from this locality is of the same age as that from Monterey (see Hanna, 1928a: 975). Monterey, Monterey county The samples said to come from Monterey almost certainly come from the outcrop of the Monterey Shale four miles east of Monterey, the locality of the type Delmontian Stage. According to Hanna (1928a), this dates from about the boundary between the middle and the late Miocene, probably from the earliest late Miocene. Wornardt (1967: 7), however, says that the Monterey diatom flora is from the top of the upper Miocene and that the same diatom assemblage occurs elsewhere in California. More recently Barron (1976a) has shown that Hanna’s is the correct date. ‘Santa Lucia’ Specimens said to be from this locality presumably come from one of the numerous deposits of Miocene diatoms that outcrop on the inner, eastern side of the Santa Lucia Moun- tains, Monterey County (see Hanna, 1936). According to Wornardt (1967) these are late Miocene in age, but Barron (in litt., 1991) says that upper middle Miocene diatomaceous rocks are more common in this area, although samples from there could be upper Miocene. Santa Maria, Santa Barbara County One cannot be certain whether the material collected in the nineteenth century and labelled as from Santa Maria, Califor- nia, came from the lower upper Miocene Monterey formation or the uppermost Miocene to lower Pliocene Sisquoc forma- tion (for the age of this see Barron & Baldauf, 1986), both of which are exposed in the Santa Maria district (Woodring & Bramlette, 1950). The Sisquoc formation is, however, more widely and more accessibly exposed there and is thus the more likely source. Paradise Cove, Malibu, Los Angeles County Malibu, Los Angeles County Specimens labelled as from Malibu presumably come from the outcrop of Miocene material at Paradise Cove. The most likely age for this is early in the late Miocene (Barron in litt., Por): Temescal Canyon, Santa Monica, Los Angeles County Barron (in litt., 1991) has found late Miocene diatoms from this locality. Malaga Cove, Los Angeles County The outcrop of upper Miocene diatomiferous rock at Malaga Cove is the source of the ‘floating fossil’, a block of diatomite found on the beach at Santa Monica, Los Angeles County; it is also the nearest outcrop to Redondo Beach (San Redondo), which is four miles to its north-west (Hanna, 1928b, 1936; Laporte, 1936). Specimens labelled as from Santa Monica, Redondo Beach, or San Redondo are all from this outcrop. Both the diatomite-rich upper Miocene Val- monte Diatomite and the uppermost Miocene to lower Pliocene more mud-rich Malaga Mudstone are exposed at Malaga Cove (Barron in litt., 1991), but the samples studied by diatomists almost certainly all came from the Valmonte Diatomite. Los Angeles, Los Angeles County The upper Miocene Valmonte Diatomite has extensive out- crops in the suburbs of Los Angeles, not only at Malaga Cove but also in the area of the Palos Verdes Hills and San Pedro. The specimen with no more precise locality than Los Ange- les, and those from any of the following three localities almost certainly came from this formation (Barron in litt., 1991): Palos Verdes, Los Angeles County Channel Road, San Pedro, Los Angeles County San Pedro, Los Angeles County Newport Beach, Orange County Specimens labelled as coming from Route 101, Newport, as well as those labelled only Newport or Newport Beach, come from the middle and upper Miocene Monterey formation exposed there (see Barron, 1975, 19766). Mexico Maria Madre Island Samples of diatomite of high purity were obtained from the bank of the Arroyo Hondo, about 2-3 miles inland from the north coast of this island (see Hanna & Grant, 1926). The material is late Miocene (see McCloy et al., 1988). New Zealand Oamaru, Otago Edwards (1991) gives detailed descriptions of all the known outcrops of the Oamaru diatomite and diagrams of the stratigraphic columns at these localities. He shows that almost all the diatomaceous rocks are late Eocene in age, but that the uppermost ones exposed at Forrester’s Hill and at Mavor’s Farm are from the earliest part of the Oligocene. Long before the publication of this account of the Oamaru diatomite, Edwards assigned code numbers to each bed at each locality, prefixing these with letters indicating the local- ity, and Doig (1967) indicates how these relate to the names for outcrops used by earlier diatomists. The following is a list of the names of the outcrops from which specimens of Rutilaria are recorded together with the code designation as given by Edwards (1991): Allan’s Farm = AF3 Bain’s Farm = BN7(3), BN9(3) Bain’s Farm, lower = BN9(3) Borrie’s = PP (one or more unspecified outcrops with this prefix) Cave Valley = CS1 according to Edwards (1991: 57) Cormack’s Siding = CS1 Dick’s Farm ?= Jackson’s Well, but see Edwards (1991: 53) Flume Creek = Flume Gully Flume Gully = PP (any) Forrester’s Hill = FH2 or FH4. These two outcrops are just above and just below the Eocene to Oligocene boundary Jackson’s Farm = Jackson’s Paddock Jackson’s Hill = JP3 Jackson’s Paddock = JP3 (but a few specimens so labelled may be from JP5) Jackson’s Well (locality uncertain, see Edwards (1991: 53) Lower Papakaiyo = PP12(N) (but a few specimens so labelled may be from PP10(N) Mataura Papakaiyo = PP8(N), PP10(N), PP12(N) Railway Cutting = CS1, or perhaps CE3 or CES Totara = BNS(4) Troublesome Gully = TG2, or possibly TG1 Williams’ Bluff = WB1 All of these exposures, except FH2, are late Eocene in age. There are many specimens without any more precise locality than ‘Oamaru’. These include specimens in Grove’s and Sturt’s collections that were from the original sample on which their account of the diatom flora of the Oamaru diatomite was based. According to Lautour (1889), this came from the outcrop CS1. It is very unlikely that any of the specimens labelled simply ‘Oamaru’ came from the upper- most diatomites at Forrester’s Hill or Mavor’s Farm, which are the only ones above the Eocene to Oligocene boundary. These specimens are therefore listed as late Eocene. In the distribution records for the individual species, the outcrop, when this is indicated, is given as on the label of the specimen. The list above shows which of the beds delimited by Edwards (1991) are referred to by these outcrop names. South Atlantic Falkland Plateau, Vema cruise 12, core 46, 47° 28.7'S, 59° 20.6’W, depth 1167 m, 630 cm from top of core Middle Eocene with a strong admixture of Paleocene and early Eocene (Fenner in litt., 1984). Falkland Plateau, Vema cruise 17, core 107, 51° 08'S, 54° 22'W, 1525 m depth, 50 cm, 120 cm, and 175 cm from top of core All middle Eocene (Fenner in litt., 1984). Falkland Plateau, Vema cruise 18, core 104, 53° 01'S, 52° 52'W, 2880 m depth, 330-333 cm from top of core Middle to late Eocene (Fenner in litt., 1984). R. ROSS Falkland Plateau, Vema cruise 18, core 112, 51° 40'S, 48° 29'W, 2429 m depth, 100 cm from top of core Lower Oligocene (Fenner in litt., 1984). Falkland Plateau, Conrad cruise 12, core 237, 47° 45.7'S, 57° 38.5'W, 3650 m depth Eocene, probably middle or late, rather than early, Eocene. Barbados The fossil diatoms from this island occur in the Oceanic Beds, which range in age from the middle Eocene to the early Miocene. Specimens of Rutilaria with a locality no more precise than ‘Barbados’ may have come from any age within this range. However, the only samples containing diatoms that have been dated as Miocene are from Conset Bay, and the species present in samples from other localities that have not been firmly dated suggest that none of these are older than the Oligocene. It seems probable that this is also the case for specimens with the locality given as nothing more than ‘Barbados’. All such specimens are therefore regarded as coming from within the range middle Eocene—Oligocene. Cambridge Estate All the specimens from this locality come from material distributed by C. Johnson in the middle of last century. The Radiolaria on two strewn slides of this material indicate that its age is middle Eocene (Riedel in Holmes & Brigger, 1979). There is uncertainty about the locality from which this material came (see Robinson, 1941). Chimborazo Brun (1896) had material from this locality, and there are specimens from it mounted by Brigger at BM and CAS, but there is no information about the site from which it came nor about its precise age. Clealand Brun (1896) records a specimen from this locality, but there is no further information available about its provenance. Conset A sample from Conset collected by J.H. Robinson was sent by Holmes & Brigger (1979) to W.R. Reidel, who dated it as early middle Eocene on the basis of the Radiolaria it con- tained. Robinson (1936) gives details of two localities in Conset from which he had ob.ained samples containing diatoms. Robinson and F.W. Adams collected in Barbados early in 1936 (Robinson, 1937) and obtained further samples from the Conset area. There are strewn slides prepared from these samples and mounted by F.W. Adams in his collection now in BM. Dr J.A. Barron of the U.S. Geological Survey has kindly examined these for me and gives the following ages for them: Manjack Hole, Conset Bay; middle Eocene College Hill, Conset Bay; early Oligocene Burnt Hill, Conset Bay; early Oligocene St Mark’s, Conset Bay; late early Miocene REVISION OF RUTILARIA GREVILLE (BACILLARIOPHYTA) Railway Track, Conset Bay; late early Miocene The only specimen of Rutilaria on these slides is one of R. elliptica Greville from Burnt Hill. In addition Brigger mounted many specimens from these samples, but gave only Conset as their locality; they may have come from any one of the samples from there. It would seem that he assumed that these samples did not need to be distinguished from one another. These specimens include all the known specimens of Rutilaria flabellifera R. Ross and the only specimen of R. szakalensis Pantocsek from Barbados. The sample sent to Riedel presumably came from Manjack Hole. It seems rea- sonable to assume that species known elsewhere only from the Miocene and recorded from Conset but nowhere else in Barbados come from one of the lower Miocene samples. Examples are Rutilaria szakalensis, Briggera haitensis, Entogonia formosa and E. jeremiana. Rutilaria flabellifera also has not been found elsewhere on Barbados. There is little doubt that it is an evolutionary successor of the middle Eocene R. cantabrigiensis, and that it therefore comes from an early Oligocene or an early Miocene sample rather than a middle Eocene one. Joe’s River All the specimens from this locality come from material distributed by J.H. Robinson, who gives details of the site from which it came (Robinson, 1938). According to Riedel, the Radiolaria in this material indicate that it comes from the upper Eocene to Oligocene boundary (Holmes & Brigger, 1979). Mount Hillaby No details about the precise site or age of the diatomite from this locality are available. Springfield Robinson (1941a) gives details of the site of the quarry that is the source of the diatomite from this locality, and also a list of species found there. This list suggests that the most probable age for this deposit is late Eocene. It is probable, but not certain, that the nineteenth century samples from Springfield came from the same quarry as Robinson’s material and specimens from there have accordingly been considered to be of late Eocene age. Haiti Jérémie Truan & Witt (1888) give details of the source of the fossil material from this locality. A sample of this was dated by Riedel as early Miocene on the basis of its Radiolaria (Holmes & Brigger, 1979). Ross & Sims (1985: 284) expressed doubts about this dating, but now that it is known that some samples from Conset Bay, Barbados, are early Miocene in age (see above) there is no longer any reason to question its accuracy. Gonaives There are specimens from fossil material from this locality in Brun’s collection at G, but no details about the precise site or about the age are available. The specimens include one of Rutilaria grevilleana subsp. monocellata, otherwise known only from the lower Eocene of the Blake Plateau, North Atlantic, and one of R. amplectans, otherwise known from material from the middle to upper Eocene boundary in the Indian Ocean and from the upper Eocene of Oamaru, New Zealand. An Eocene age is therefore assumed for these diatoms. North Atlantic Blake Plateau, 30° 08.54'N, 76° 06.74'W, 2665 m depth, Deep Sea Drilling Project Hole 390A, core 7, section 4, 129-131 cm This sample is from the lower Eocene (see Gombos, 1982). Bermuda Rise, 30° 53.39'N, 67° 38.86'W, 5125 m depth, Deep Sea Drilling Project Hole 6 The specimens from this locality, including those examined with the scanning electron microscope, were all selected by A.L. Brigger. He had samples from core 3-4, 72-78 cm down to core 6-3, 20-24 cm. All the material throughout this range is middle Eocene in age (Berggren, 1969: 606). Labrador Sea, 53° 19.876'N, 45° 15.717'W, 3870 m depth, Ocean Drilling Programme Hole 647A, core 19R, section 1, 125-127 cm This sample is from the lower Oligocene (Monjanel, 1987). TAXONOMIC ACCOUNT The terminology used in the descriptions of the genus and the species is that given in Anonymous (1975) and Ross et al. (1979), with a few additions and one modification. ‘Projec- tion’, ‘interrupted striae’ and ‘sibling valve’ are used in the sense defined by Ross & Sims (1985). ‘Marginal spine’ and ‘superficial spine’ are used in the sense defined by Ross (1990). The marginal spines are usually slightly inset from the margin of the valve face and form two rows, one along each margin, that are separate throughout. In some species with very narrow projections, however, the two rows, one on either side of the central portion of the valve and the proximal parts of the projections, meet and continue as a single row along the centre of the distal parts of the projec- tions (see, e.g.,Plate VIII (e)). These spines on the mid-line of the distal parts of the projections are nevertheless also called marginal spines as they need to be distinguished from the superficial spines that occur in some species sparsely scattered on the central portion of the valve and the proximal parts of the projections. A structure peculiar to Rutilaria 1s the periplekton, a modified labiate process consisting of a vertical tube, the stem (caulis), from the top of which two arms (brachia) project horizontally and encircle the stem of the periplekton of the sibling valve, forming a ring (annulus) (see Plate 2 (d)). In a number of species there is a flange 10 (margo alata) along the outer side of the arms that form the ring of the periplekton (see, e.g., Plate XII (b)). The length of the pervalvar axis, i.e. the depth of the frustule, is considered to be the distance between the bases of the periplekta of the two valves; the periplekta, and the eleva- tions present at the apices of many species, are not included. Round, Crawford & Mann (1990: 48-49) have criticized the terminology for the girdle bands proposed by von Stosch (1975) and adopted in Anonymous (1975) and Ross et al. (1979). They point out that there is no general criterion for distinguishing between copulae and pleurae as defined by von Stosch and that the change in the morphology of the girdle bands between the more advalvar and the more abvalvar is often gradual, not abrupt. They therefore suggest that all girdle bands be termed copulae, the one immediately adja- cent to the valve, which usually differs somewhat from the others, being called the valvocopula, the others being num- bered in abvalvar sequence. This suggestion is followed here and the girdle bands are referred to as valvocopula, copula II, copula III, etc. Most of the descriptions of the girdles are incomplete. Almost all the species of Rutilaria are fossil and in fossil material complete girdles attached to valves are infrequent to rare. Also, specimens of bipolar species mounted in girdle view for light microscopy almost invariably lie with the apical axis parallel to the slide on which they are mounted. When specimens are in this position, it is often impossible to see whether copulae are open or closed. This can be seen on scanning electron micrographs but very few of these showing specimens with intact girdles have been avail- able. Five species are divided into two infraspecific taxa and these are given the rank of subspecies. The differences in morphology between the two subspecies of one species are very slight, appreciably less than those between the taxa that are recognized as distinct species. In four cases the two subspecies do not occur in the same fossil deposits. In two of these, Rutilaria hannai R. Ross and R. tenuicornis Grunow, the two subspecies are separated not only geographically but also in time; they do not occur in the same geological period. There may also be a slight difference in age between the fossil deposit at Inza, Russia, and the Danish Fur formation in which the two subspecies of R. minima R. Ross have been found. The two subspecies of R. grevilleana (Walker & Chase) R. Ross are both present in the early Eocene but their known occurrences at that time are well separated geographi- cally. The length of time during which both were present is, however, uncertain as the age of one of the two deposits in which R. grevilleana subsp. monocellata R. Ross has been found, that at Gonaives in Haiti, is not known. Both subspe- cies of R. areolata Sheshukova-Poretskaya occur together in the late Eocene of Oamaru, New Zealand, but their other records are from different localities and these may not overlap in time. Diatomists have, for the most part, used the rank of variety for infraspecific taxa, but most of those recognized have been taxa similar in kind to the phenodemes found in Sellaphora pupula (Kiitzing) Mereschkowsky (Nav- icula pupula Kitzing) and described by Mann (1984). These clearly have a different status from the infraspecific taxa recognized here, which seem to be comparable with those treated as subspecies in higher plants by those authors who recognize infraspecific taxa of that rank (cf. Hamilton & Reichard, 1992). In the synonymies for each species and subspecies all the accounts of the taxon that are accompanied by illustrations R. ROSS are cited. An appreciable number of records are shown by the figures that accompany them to be based on misidentifica- tions. In consequence there are very few records not accom- panied by figures on which one can rely, and only these few are included in the synonymies and the distributions. A few published figures are not detailed enough for certainty as to the identity of the specimen shown. References to accounts accompanied by such illustrations are given under the taxon to which they probably refer preceded by a question mark Gy. Drawings of each taxon, as well as photomicrographs and, where available, scanning electron micrographs, are pro- vided. Because the depth of focus obtainable with the light microscope is so limited, a photomicrograph cannot show all the morphological detail needed to distinguish a taxon, whereas a drawing can. With one exception, the scanning electron micrographs reproduced here were taken in BM and are preserved in the collection there. Their reference num- bers are given in the explanations of the figures. The herbarium or institution in which the holotype of a new taxon is conserved is indicated by the acronyms given in Index herbariorum (Holmgren, Holmgren & Barnett, 1990) and also by Fryxell (1975). A number of the holotypes conserved in BM are on strewn slides or selected slides with many species present. When this is the case the citation of this slide is preceded by ‘in’. The position of the holotype specimen on the slide is given in the documentation of the diatom collection in BM. In the distributions given for each species or subspecies, all the specimens that I have seen are listed, apart from the very few which are not localized. In these lists also the institutions in which the specimens are conserved are indicated by the acronyms given in Index herbariorum. In addition, the scan- ning electron micrographs taken and preserved in BM are listed. With a few exceptions, records from the literature are given only when they are from a locality from which no specimens have been seen. The few records attributed to ‘personal communication’ are based on unpublished micro- graphs kindly sent me by colleagues. The records are arranged according to the geological age of the material in which the specimens occurred and, within any one geological period, in the geographical order adopted in the section on the sources of specimens (pp. 3-9 above), where fuller details about each locality are given, including the evidence on which specimens from there have been assigned to a particular geological period. Where there is doubt about the geological age of material from which specimens come, the range of age within which it might have been deposited is given in the form ‘middle Eocene—Oligocene’; where it is known to come from very close to the boundary between two periods, its age is given as, e.g., ‘late Eocene to early Oligocene’. As men- tioned above, records that are probable but not certain because they are based on inadequate illustrations are pre- ceded by a question mark. In some cases I believe that the locality given on the label of a specimen is an error; such records are enclosed in square brackets (‘[]’). The order of the species in this account is such as to bring together those that seem most closely related, and those in each group are arranged in the order of their appearance in the fossil record, with one exception. It was not until this paper was reviewed by Dr J.A. Barron that I learnt that the date attributed by Jousé (1955) and Glezer (in Glezer et al., 1974) to the deposit at Kamyshlov was incorrect. By that stage all the figures had been prepared for publication and it REVISION OF RUTILARIA GREVILLE (BACILLARIOPHYTA) was not possible to move the account of Rutilaria kamyshlov- ensis R. Ross so that it preceded that of R. interrupta R. Ross instead of following that of R. hannai R. Ross. RUTILARIA Greville in Q. JI microsc. Sci., new ser. 3: 227 (1863). Syndetocystis Ralfs ex Greville in Trans. microsc. Soc. Lond., new ser. 14: 125 (1866). Syndetoneis Grunow in Bot. Zbl. 34: 36 (1888). — De Toni, Syll. alg. 2: 1019 (1894). Frustules united in inseparable short chains. Valves normally bipolar, circular, elliptical, broad lanceolate or sub- hexagonal, often with projections that may be long and subcapitate or capitate. Small apical elevations present in some species. A sub-circular to circular hyaline central area present, the rest of the valve areolate, the areolae poroid, in radial striae or irregularly arranged. In the centre of the valve a periplekton, a modified rimoportula, its internal opening a straight slit across a slightly raised papilla, its external part consisting of a vertical tube, the stem, with at its upper end two lateral arms that form a ring clasping the tube of the periplekton of the sibling valve. An ocellus without a thick- ened rim present at each pole on the distal face of the elevation or on the mantle. Marginal spines present in most species, sometimes with a gap opposite the central area, sometimes absent on the distal part of the projections, sometimes forming a single row along the centre of the distal part of narrow projections; occasionally two parallel rows of such spines along each margin of the valve, those in the outer row smaller and more closely spaced than those in the inner row. Scattered superficial spines sometimes present on the valve face. Cingulum consisting of two to five copulae, the valvocopula open or closed, the other copulae open. LECTOTYPE SPECIES. Rutilaria epsilon Greville (see Round, Crawford & Mann, 1990: 314, 701). Three species were included in Rutilaria when it was first described: R. epsilon, R. elliptica and R. ventricosa. R. epsilon was the earliest of these to come to Greville’s attention, and his account of the genus is based more on this species than on the others; it is accordingly the most appro- priate choice for a lectotype. The first designation of a lectotype, however, was not made until 1990. The generic name Syndetoneis first appeared in Grunow’s (1888) comments on Grove and Sturt’s account of the dia- toms in the deposit at Oamaru, New Zealand. He says of the species that they had called Hemiaulus amplectans Grove & Sturt (1887a: 76): Syndetoneis amplectans (Gr. et St.) Grun. (Hemiaulus amplectans Gr. et St.) Sicher kein Hemiaulus. Verwandt mit Ditylium, aber Biddulphia-artig mit 2 hohen Polstern und dicker, oben getheilter Centralborste, die wie bei Syndetocystis die Borste der benachbarten Schale umschlingt. Bei Syndetocystis sind die Frusteln cylindrisch. It is not easy to decide whether these remarks constitute a diagnosis of the genus Syndetoneis, giving it valid publication, or whether they refer to the species. They cannot be treated as a descriptio generico-specifica under Art. 42.1 of the International code of botanical nomenclature (Greuter et al., 11 1994) as the previously published name Hemiaulus amplec- tans has the same type. However, as Grunow points out how the taxon differs from other genera, I here take the view that his remarks are to be regarded as a diagnosis of the genus and hence that the generic name Syndetoneis and the combination S. amplectans were validly published by him. Should the opposite view be taken, then those names were validly published by De Toni (1894), who attributed them to Grunow. When Rutilaria was first described it was believed by Greville, and also by Kitton and Rylands, whom he con- sulted, that the specimens on which the genus was based were in front (girdle) view, whereas they were actually in valve view. As a result of this misapprehension the structure of the valve was completely misunderstood and the genus was thought to be related to Nitzschia, the marginal spines being equated with the keel puncta (fibulae) of that genus. In the next few years specimens in girdle view, and one at least lying obliquely, were found, and these enabled Greville (1866) to give a more accurate account of the genus, and to suggest that its affinity was with the Biddulphieae rather than with Nitzs- chia. He did not, however, give an accurate account of the periplekton but described it as ‘a central glistening nodule prolonged into two short, linear, obtuse processes’, adding that Rylands had ‘satisfied himself that of the two central processes one was straight and the other curved as in the flexure of a forefinger; and that the processes of the opposing valves were interlocked, the straight process of the one passing mutually through the curved process of the other.’ The next attempt to describe the periplekton of Rutilaria was by Jurilj (1965), who introduced that term for the structure in the centre of the valves of that genus, Syndetocys- tis and Syndetoneis. Intervening authors referred to the periplekton as ‘central peculiar nodule’ (H.L. Smith, 1872: 15), ‘nodulo centrali elevato convoluto vel tuberculiformi’ (De Toni, 1894: 1021), ‘a peculiar hooked central nodule’ (Van Heurck, 1896: 429) or ‘a peculiar central nodule pro- longed into two, short, linear, obtuse processes’ (Van Heu- rck, 1896: 433), ‘einem kurzen, knotenartigen, gewundenen oder hockeringen Forsatz, mit dem die Nachbarzellen verw- achsen’ (Schiitt, 1896: 100; Karsten, 1928: 250), or ‘poro centrali processu convoluto vel bifurcato’ (Forti, 1912). According to Jurilj (1965) the periplekton of R. radiata Grove & Sturt consists of an upright stem with, at its top, a circular loop that encircles the stem of the sibling periplek- ton. However, as can be seen from the illustration provided by Ross & Sims (1972: fig.30) and from Plate III (c), (d) of this paper, the ring of the periplekton in this species is formed by two arms whose tips overlap. This is true of all species of Rutilaria except for R. flabellifera R. Ross, which has no ring, and perhaps also R. attenuata R. Ross. Until now, almost without exception, Syndetocystis Gre- ville and Syndetoneis Grunow have been regarded as genera separate from one another and from Rutilaria. Only one species has been included in each of these two genera, although both of these species have a number of synonyms. A detailed history of the inaccuracies in the figures and descrip- tions of R. grevilleana (Walker & Chase) R. Ross, the type species of Syndetocystis, is given under that species (pp. 14-17). Also, as is pointed out under R. amplectans (Grove & Sturt) R. Ross (p. 18), the type species of Syndetoneis, the accurate figure that accompanied its original publication has misled some authors into thinking that the periplekta of two sibling valves differed. For these reasons, it was not realized 12 that differences between the type species of the two genera were insufficient to support generic separation: presence or absence of marginal and superficial spines, size and arrange- ment of areolae, and height of elevations and periplekta. Grunow (1888) thought that the periplekta of the two genera were the same but that Syndetocystis had cylindrical frustules without elevations, whereas Syndetoneis had elevations. De Toni (1894), on the other hand, realized that both had valves with two elevations but maintained their separation on the basis of a supposed difference in their periplekta. He described that of Syndetocystis accurately as having a lateral ring at its summit, but said that in Syndetoneis the periplekta of sibling valves were dissimilar, one forked, one simple. The first author to combine the two genera was Lefébure (1947), who cited Syndetoneis as a synonym of Syndetocystis without comment. Jurilj (1965) tentatively suggested that the two genera should not be separated; according to him, Syndeto- neis had a periplekton with a closed ring at its summit and Syndetocystis, which he knew only from literature, probably did so also. In this he was correct, except that the ring in both genera is not closed, as shown in his figures, but formed of two overlapping arms. These mistaken views about the characters of Syndetocystis and Syndetoneis, combined with the ignorance of the struc- ture of the periplekton of Rutilaria, prevented earlier authors from realizing that the three could not be separated at the generic level. Apart from an incidental mention by Ross & Sims (1973), this has not been pointed out until now. It had been realized much earlier, however, by Brun. In the Conser- vatoire Botanique de Genéve there is a manuscript entitled ‘Diatomées. Espéces et variétés nouvelles par J. Rataboul et J. Brun. Genéve—Moissac. 1904. Projet de publication, arrété par le mort du Mr Rataboul. J. Brun. 1905.’ In this there is the following: Rutilaria Barbadensis Rt. & Br. olim. (Syndetocystis Bar- badensis Ralfs.) Cette figure qui représente la face valvaire est le complé- ment de cette donnée par Ad. Schmidt et qui représente la face connective. Lire la notice du traité de Van Heurck (p. 432) et celle de Ad. Schmidt a la planche 173 de I’Atlas. Avec leurs écailles sur la surface valvaire et leur fort épine axiale les Ditylum se rapproche aussi de Rutilaria. Cette espéce appartient en réalité aux Rutilaria dont elle a tous les caractéres. La forme arrondie de sa valve ne permet guére d’en faire un genre 4 part, car certains types de ce genre ont une forme hexagone ou ovale, déja plus ou moins arrondie. Voir le ‘Diatom.’ I 10/2 et II 5/19. 4492. The figure referred to in this quotation was not with the manuscript, but 4492 is the number of a microscope slide in Brun’s collection. This slide has on it selected specimens from Gonaives, Haiti, including one of R. grevilleana subsp. mono- cellata R. Ross and one of R. amplectans (Grove & Sturt) R.Ross. The figure was presumably of the former. It was over a century after Rutilaria was first described before it was pointed out that an ocellus was present at each pole of the valve. This fact was first mentioned by Simonsen (1972: 50), and an illustration showing one was provided by Ross & Sims (1973: fig. 50), although reproduction of this is so bad that it can scarcely be made out. As the figures in this paper show (e.g. Plate I (b), (f), Plate V (d), Plate VI (c), Plate XIX (d)), all the species that it has been possible to investigate with the scanning electron microscope, including R. ROSS R. grevilleana and R. amplectans, have ocelli. As compared with the ocelli of such genera as Auliscus and Eupodiscus, those of Rutilaria are usually small and do not have a well developed rim. They are thus intermediate between the ocelli of these genera and the ocelluli of the Cymatosiraceae (Hasle, von Stosch & Syvertsen, 1983: 12). A number of the species of Rutilaria are remarkable for their range of outline. The longest specimens of these species have capitate projections each of which is more than twice as long as the central portion of the valve, and there is a continuous gradation between these and specimens with elliptical, broad lanceolate or subhexagonal valves and no projections whatever. Most of these valves without projec- tions are almost or quite as broad as those with long projec- tions. R. radiata Grove & Sturt (see Fig. 19), R. philippinarum Cleve & Grove, R. elliptica Greville and R. obesa Cleve (see Fig. 76) all show such a range of outline, and there are indications that R. interrupta R. Ross and R. hannai R. Ross do so also, but not enough specimens of these species have been found for this to be certain. That there is such a wide continuous range of outline of specimens otherwise indistinguishable is only obvious when a considerable number have been seen. As a consequence, specimens from different parts of the range of outline of the same species have been regarded as belonging to separate species. Rutilaria is a genus with a very long history. There is a record from the Campanian, but this is doubtful (see p. 32 below). It was certainly present in the Paleocene, and it has persisted until the present day. The two living species, R. tenuicornis Grunow and R. philippinarum Cleve & Grove, are both very uncommon members of the neritic plankton of tropical and sub-tropical seas. This seems to have been the habitat of the genus throughout its history, and its fossil representatives are never common in any of the deposits in which they occur. Some species have a long fossil history, the two living species the longest, from the middle Eocene to the present day. Others, however, occur through a very limited time interval and are also sufficiently frequent, although not common, to be of use for stratigraphic purposes. KEY TO THE SPECIES I, ‘\Nosmarpinal spines, 34)..25...220as5s-:Reeeeeet rete sadn: eee 2 Mareinallspines)present csc. -ce-secsreere “acu sesearadese- eeeeee ee Rer il 2 Elevations more than 10 wm tall .................... 2. amplectans Elevations/nomore) than’ jumiltallly 6oe-s-eaese-e caer eee eee 3) 3” .Centrallarea not reaching Valve mareiny + -..-----cs-0- aaa eee 4 Centrallarea teaching, valve miateinl ereeees ene eee eee eee 6 A Superficial spinesimany \:.-0--4: -erceeeee eee meee 3. erinaceus Supenticialispinesione \..2.tassssetasesseacee as eae eee eee eee 5) 5 Valve with costae inset from the margin and uniting to become GemtraliGistally sic. siete aadet pcbenadtosse east. eee 9. minima Valve without any Costae ........cseqsse-- spe oeee spe 17. lanceolata 6 Striae and areolae 12-13 in 10 wm; ring of periplekton c. 10 pm UMGIAMICIEr eceteorens. See bese ooeaneee dame asc eee aes 17. lanceolata Striae and areolae 17 or more in 10 wm; ring of periplekton at leastel 7 emiiniciameter, passa ceeeeeereaeeeeaese see 5. interrupta 7 Valve c. 10 wm wide and tapering uniformly from centre to apices; areolae near central area 6-7 in 10 um.... 25. attenuata Valve more than 10 wm wide, or with projections distinct from REVISION OF RUTILARIA GREVILLE (BACILLARIOPHYTA) the central portion, or with areolae 10 or more in 10 wm close to the central areal 2.50: cweee Rewt ge ocpeedeoess Was tae > «Tease ho eee 8 8 Flange on ring of periplekton extending beyond the central area opposite the sibling periplekton as far as superficial spines on the sibling valve Flange on ring of periplekton, if present, not extending beyond BIG COMMMAM ATC AMEE cence tach redseatec wacicicchcnveesceneaqhesedta Sos 10 9 Valves less than 15 ym broad; striae and areolae 15 or more in MDIREL mss Sconce tt Roe Siaes actos nernasidcisee''e 18. cantabrigiensis Valves more than 18 ym broad; striae and areolae 10 or fewer in MP RPUT Tete op 0 Sok > ach uetnedaes stewdttans Sec tcaake ee deers 19. flabellifera 10 Ring of periplekton with equal arms and without a flange Ring of periplekton with unequal arms or, if apparently equal, with a flange 11 Striae and areolae 2.5-5 in 10 pm Areolae within striae 15 or more in 10 wm _..................04 i 12 Areolae partly in much interrupted radial striae, mostly irregu- PAMMMESLLAN ECM ences: dat cnasddsneessciiqoaadt spade 4. limoniformis Areolae in continuous radial striae, at least on the central PORRUUNORE OTT CIV AIC. os tos asnodeoseceracckiscnase duos @iiosniat 6 «aseye ce 13 13 Striae close to the central area no more than 10 in 10 pm ....... + doce 3 CABG See BOSE EEE ee REE RARER Oc Orne LES eee 6. radiata Striae close to the central area 15 or more in 10 pm ......... 14 14. Margins of central portion strongly convex; no raised apical EU AON Se. sere Ree rep rd sto «tp etNp oadvdadaein cSdcaebnewghascless 7. hannai Margins of central portion not strongly convex; raised apical CLEVAMLONS PLESEML ..0.sncpaseectera’encawtaslelseas oes 8. kamyshlovensis 15 Marginal spines 15 or more in 10 pm ...............5. 13. hyalina Marsinalspines 12 or fewer In 10 pum «..2.... 0.000 screrecaaee sins 16 16 Distal marginal spines with obvious longitudinal costate exten- sions Distal marginal spines, if present, without obvious longitudinal COMIENG GZUGI SONIC: déabehe daectecscoantcos see ce cpCheEesbce a tease eae 20 17 Marginal spines in a double row along each margin of the valve, the outer row of very small spines often not visible with the light microscope, the inner rows sometimes uniting distally to form a single central row; outer and inner rows forming distal longitu- BUM PAICOSEAG tele ciaity Seve den quotas tcies axereciacote simcfenee's tee 14. briggeri Marginal spines in a single row along each margin of the ARMM a aoe = fe cedure greta des Sesseadaceeesatepscer