DITHYROCARIS. 



135 



the right-hand valves is ou the left hand in the plates, and the curved edge 

 {ventral or lower) of the right-hand valves is on the right hand in the jDlates. 



We propose to commence the descriptions with the more simple and smooth 

 forms, and to take successively those with ridges and other surface oima- 

 mentation. 



In arranging the plates and their figures we at first looked up the specimens 

 that had been already published, and began with the apparently simplest forms. 

 The arrangement of the drawings, however, was greatly influenced, of course, by 

 the incoming of specimens at different times and from different sources. 



Table of the Distribution of Dithyrocaris and Allied Genera. 





C! o 



CAEBONIFEKOUS. 

 1. Dithyrocaris glabra, 1873, Woodward and Etheridge. 



— omZjs, 1873, W. aud E 



— ffraiiulata, 1S7S, W. and E 



— lestudinea, 1835, Scouler 



— Colei, 1813, Portlock 



— orbicularis, \8^^,VoTi\oc\i 



— ^ricorra/s, 1835, iScouler 



— funiculata, 1898, sp. uov 



— ScoiJeri, 1842 or 1844., M'Coy 



— insignis, sp. nov 



Calyptocaris striata, 1871, Woodward, sp 



12. Ghaenocaris tenuistriata, 1844, M'Coy, sp 



— I^OM»yu', 1898, sp. uov 



Dithyrocaris lateralis, 18ol,M'Coy 



— Dunnii, 1898, sp. nov 



— iVet7so«j, 1898, sp. nov 



— carbonaria, 1870, Meek and Worthen 



Rhachura? «ewo«a, 1878, Scudder 



mbbertia orbicularis, 1898, gen. et sp. nov 



DEVONIAN. 



Carapace — 20. Dithyrocaris Belli, 1871, Woodward 



r21. — iLoc7«, 1864, Ludwig 



22. — breviaculeata, 1864, Ludwig.. 



23. — ir«yse«, 1884, Clarke 



24. — .^ Jrt«c/iei, 1856, Riimer 



25. Mesothyra Oeeani, 1883, Hall and Clarke 



26. — i%j/M«;, 1863, H.all 



27. Chosnocaris ? Richteriana, 1898, sp. nov. .. 



C3 



X 



Note.— la our "Seventh Report ou the Palseoz. Phyllop.," 1889 (' Brit. Assoc. Eep.,' 1890, 

 p. 65), we referred to two specimens of Dithyrocaris, in M. Paul Lebesconte's Collection at Einiies, 

 from Lower Silurian Eocks, but have not yet been able to study them fully. 



