152 Dr. H. JFoodivard — Carboniferous Trilohites. 



Fig. 4:a.—Brachylepas cretacea. Specimen obtained and developed by Dr. Arthur 

 Rowe, M.S., M.R.C.S., F.G.S., from the Chalk of Margate. Enlarged 

 three times natnral size. Original preserved in Dr. Eowe's cabinet, c. carina ; 

 r. rostrum; i.s., i.s. imbricated scales at base of capitulum. 



Pig. 4i. — Sub-lateral scales, enlarged six times natural size. From the centre of 

 series just below the latus (see restoration in text, Fig. 3, /). 



Fig. 5. — Pyrgoma angUcum, Leach (viewed from above). From the Coralline Crag, 

 Eamsholt, Suffolk. Enlarged four times natural size. Eecent : Great Britain, 

 Europe, Cape de Yerde. (Copied from Darwin's " Balauidie " : Pal. Soc. 

 Moil., 1854, tab. ii, fig. la.) 



II. — Note on some Carboniferous Trilobites. 



By Henry Woodward, LL.D., F.R.S., F.G.S. 



(PLATE VIII, Figs. 6-S.) 



THE problems of life which the biologist is called upon to solve 

 present so many and such varied aspects that they are never 

 likely to become exhausted, or to weary by reason of their monotony. 

 Among these the appearances and disappearances of groups in time 

 (like the players on Shakespeare's mimic stage) are certainly not the 

 least interesting questions awaiting solution. 



In the case of the Trilobita, we are indebted to Walcott in 

 America, Hicks in Wales, Lapworth in England, Peach and Horns 

 in Scotland, Nathorst in Sweden, Mickwitz in Russia, and Holm in 

 Lapland for extending the Olenellus zone back in time to the Lower 

 Cambrian, thus giving to the Trilobites a vast increase in antiquity, 

 without by any means reaching the dawn of life of this group. 



The existence of Trilobites in the Carboniferous Limestone wasl 

 made known as early as 1809, but no upward extension has occurred! 

 during the lapse of nearly one hundred years, save their discovery 

 in the Culm of Waddon-Barton, Chudleigh, and Barnstaple, Devon- 

 shire,^ still within the Lower Carboniferous series. One is tempted 

 to ask, did they survive beyond the seas of the Lower Carboniferous 

 period, and, if not, what was the cause of their extermination ? To 

 these inquiries our researches have at present yielded no reply. 



It seems difficult to understand why the conditions which pre- 

 vailed in the seas during the slow building up of the vegetable 

 deposits of the Coal-period on the adjacent low-lying lands were 

 inimical to the life of the Trilobita, seeing that near those old lands 

 several species of small king-crabs (Limidi) were living, larger 

 Eurypterus - like Crustaceans, small aquatic forms of Cyclus, 

 numerous Brachyurans (the first lobsters), Antlirapalcemon, Pygo- 

 cepJialus (a Stomapod), with Phyllopod and Ostracod Crustaceans 

 in great abundance : apparently offering an undoubted cei'tificate as 

 to the salubrity of this marine resort. Yet the Trilobites disappeared. 



Although limited in the number of genera and species, the 

 Carboniferous and Culm Trilobites form a most elegant and attrac- 

 tive group, but they do not display that great variety of form or 

 ornamentation which characterized their predecessors in Silurian 

 times. 



1 H. Woodward, "Trilobites from the Culm of Devon" : Pal. Soc. Mou., 1884, 

 Carboniferous Trilobites, pp. 59-70, pi. x. Also Quart. Journ. Geol. Soc, vol. li 

 (1895), pp. 646-9. 



