May 30, 1895] 



NATURE 



IIS 



Ostracoda. TKe faint beginnings of other great groups were 

 also indicated, sucli as the Macniiiran-deca|xjds represented by 

 Anthrapalinuon ami other forms in the Coal Measures; the 

 Stomatopods by Pygoceplialus Cooperi, the Ainphipods by 

 Gampsoiiyx , both in the Coal Measures ; and by Prosoponiscus 

 in the Permian. Lastly, the Cirripedia, by the anomalous form 

 Tiirrilepas, from the Wenlock Limestone. 



" In November 1S66, I laid before this Society the evidence 

 upon which I based my arrangement of the /'/tvj^w/^and Limii/i 

 in one order, for which I adopted Dana's very a[)propriate name 

 of Merostoniata (or 'thigh-mouthed' animals) — e.vpanded to 

 include all those ancient crustaceans comprehended in the two 

 sub-orders of Eurypterida and .\i|)hosura, and forming two groups 

 of long-bot.lied and short-bodied forms, (^uite parallel to the 

 Brachyoura and Macroura in the Decapoda ; even the inter- 

 mediate forms —corresponding to the Anomoura — being paral- 

 leled by the Hemiaspida; (Neniiaspis, Pseiidoiiisciis, i^c). This 

 group formed the subject of a monograph published by the 

 PaUvontographical Society ( 1865-1878) comprising 17 genera and 

 84 species — 69 of w hich are Pala.'ozoic in age. The integrity of 

 this group, founded on the researches of Huxley, Salter, Dana, 

 Hall, and many others besides myself, has been firmly main- 

 tained, although many attempts have since been made tcj detach 

 it from the Crustacea and place it with the Arachnida. For 

 instance, it was proposed by Dr. Dohrn, in 1871, to include the 

 Merostoniata in a still larger division, under Haeckel's term 

 Oigantostraca, which was made by expansion to embrace the 

 Merostoniata and the Trilobita, and to be placed between the 

 Crustacea antl the Arachnida. 



T»«c-;»r» y^o«ev 



Pm-MMB^I 



" In arguing for their retention before this Society in 1871 I 

 wrote: — 'Take aw.ay the trilobita from the pedigree of the 

 Crustacea, an<l I submit that one of the main arguments in favour 

 of evolution to i)e ilerived frnni the class, so far from being 

 strengthened, is destroyed. Krom what are the Crustacea of to- 

 <lay derived ? Are we to assume that they all descended from 

 the phyllopods and ostracods — the only two remaining orders 

 whose life-history is conterminous with that of the trilobita ? 

 Or are we to assume that the arachnida are the older class?' 

 ' If,' says I'rit/. Muller, ' the rrustacea, insecta, myriapoda, and 

 iirachnida are indeed all branches of a commcin stock, it is evident 

 that the water-inhabiting and water-breathing Crustacea must be 

 regarded as the original stem from which the other terrestrial 

 clas.ses, with their tracheal respiration, have branched off.' 



" In the above-quoted paper I pointed out that the young 

 I.iniiihn, when it quits the egg, has the hinder body as large as 

 the head-shielil, and the nine segments composing it are most 

 clearly marked out, the abdiiminal spine being quite rudimentary 

 and forming in fact the gth .segment. This is the so-called 

 ' Triloiiten-sladiiim' of Dohrn. 



" ' At this stage,' says I'.ickard, ' the young swim briskly up 

 and down, skimming about on their hacks by flapping their gills, 

 not bending their bodies.' This locomotion of the young 

 l.imuhis, by swimming upon its back, near the surface of the 

 water (by means of its gill feet), agrees very closely with the 

 habit of .4/>«f, of Chirorep/ia/iis.rmi Artemia, and is extremely 

 suggestive of its affinity to the phyllopoda, with which, at this 

 stage of its exi.stence, it has many points in common, as well as 

 with the trilobita. 



NO. 1 



jj:): 



VOL. 



52] 



" It is interesting to notice that the Xiphosura (king-crabs) — 

 which furm the surviving representatives of this ancient order of 

 the .Merostoniata, and are so widely distributed in the Coal 

 Measures of North America, Britain, &c. — have likewise been 

 discovered as far back in time as the Upper Silurian of Lanark- 

 shire, being represented by a small form which I named and 

 described, in 1868, NeoUntiilits fakaltts^ having eight thoracic 

 segments ap])arently free and movable, but wanting the tail-spine, 

 which probably was developed later in life, or may have been 

 represented b)" an extremely short terminal ]ilate, as we see is 

 the case in the young larval I.tmn/tis. Thus the earliest fossil 

 king-crab known probably resembled closely the free-swimming 

 larva of the li\ ing king-crab as it leaves the egg. 



"As to whether the Eurypterida — with their evidently aquatic 

 branchiated respiration, their jaw-feet provided with swimming- 

 (not walking-) extremities — are in the direct line of ancestral 

 relationship to the recent scorpions, I may refer again to my 

 paper ' On some Points in the Structure of the Xipho.sura,' iSic. : 

 — ' This is one very strong argument, to my mind, in favour of 

 the higher zoological position o{ Pterygotus — that, beingextremely 

 larval in its anatomy, it consequently possessed the capacity for 

 further development, and so has been modified and disappeared* 

 — its latest representatives being met with in the Coal Measures, 

 where the then earliest known exani])les of fossil scorpions had 

 also been found. But the discovery, almost simultaneously, by 

 Thorell and Lindstnim in Gotland ; by B. N. Peach in .Scotland ; 

 and by Whitfield in North America (in 1885) of actual pul- 

 monated land scorpions in rocks of Upper Silurian age (as far 

 back, in fact, in geological time as the earliest known occurrences 

 of Plevygottis, Slimonia, and Eniyptenis) indi- 

 cates that the air-breathing scorpions were 

 I I derived from a sti/t earlier and as yet undis- 



- ' covered aquatic progenitor po.ssibly in Cambrian 



or pre-Cambrian times. 



" Simultaneously with the commencement of 

 my own work on the Merostoniata, J. W. Salter 

 undertook a monograph on the British Trilobites 

 for the Pala;ontographical Society in 1864. 

 No one who takes up this fine work of our old 

 friend can avoid a feeling of regret that Salter's 

 valuable life and splendid palxontological kni^w- 

 ledge should not have been longer spared to us 

 to carry on to its completion this most important 

 service. 



'■ P'ollowing up the progress of our knowledge 

 "f the trilobites, I may note that Dr. Henry 

 Hicks made his first communication to this 

 Society in 1865 on the genus Aitopoleniis, and 

 between 1871 (when he came to London from 

 the happy hunting-grounds of St. David's and 

 joined the Geological .Society) and 1876, he 

 communicated to this Society a series of papers on the faunas 

 of the ' Menevian,' the Lingula Flags, Tremadoc Slates, and 

 Arenig series, giving descriptions of no fewer than thirty-four 

 species of trilobites, belonging to eighteen genera, from those 

 ancient rocks. 



" But numerous as are these additions to our knowledge of the 

 trilobites of Wales, they only represent a part of Dr. Hicks's 

 discoveries, many of which were announced by Salter ; the most 

 important being that of the finding of a large Paradoxides at St. 

 David's, jiroving the existence of a Middle Cambrian or ' Para- 

 dox ides -7.01^,' coextensive with the vast area over which these 

 early rocks have been observed, and occupying a [wrsistent 

 horizon throughout Eurojie anil America. 



" A brief reference must here be made to the papers published 

 by that excellent geologist and naturalist, the late Thom.as Belt, 

 K.G.S., in 1S67 and 1868, on new trilobites from the Upi>er 

 Cambrian rocks of North Wales, anil on the Lingula Flags or 

 Ffestiniog group of the Dolgelly District, with figures and de- 

 scriptions of four species of Oleniis {non-CoiiOiOryphe) OiWd four 

 species of Jgiiostiis from Dolgelly. In 1888 I was so fortunate 

 as to be able to record the first discovery of trilobites ( Coiioeorypke 

 viola) in the Longmynd Group, Penrhyn quarries, Bethesda, near 

 Bangor, in North Wales. 



"The remarkable fauna of the Olenelliis or Low'est Cambrian 

 zone, originally discovereii in .Vmerica by Dr. Emmons in 1844, 

 was first recognised in Europe by the late Dr. Linnarsson in 

 1S71, in the basal zones of the Cambrian near Lake Mi'isen in 

 Norway, but its typical genus Olenelliis vim then referred by him 

 to the allied but more recent genus Paradoxides. This referenc 



