DITHYROCARIS. 



135 



the right-hand valves is on 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 plates. 



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

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

 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. 



c3 

 ■— 



o 



c 



Carapace- 



CARBONIFEEOUS. 



1. Dithyrocaris glabra, 1873, Woodward and Etheridge. 



2. — ovalis, 1873, W. and E 



3. — granulata, 1873, W. and E 



4. — testudinea, 1835, Scouler 



5. _ Colei, 1843, Portlock 



6. — orbicularis, 1843, Portlock 



7. — tricornis, 1835, Scouler 



8. — funiculata, 1898, sp. nov 



9. — ' Scouler i, 1842 or 1844, M'Coy 



10. — insignis, sp. nov 



11. Calyptocaris striata, 1871, Woodward, sp 



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



13. — Youngii, 1898, sp. nov 



14. Dithyrocaris lateralis, 1851, M'Coy 



15. — Dunnii, 1898, sp. nov 



16. — Neilsoni, 1898, sp. nov 



17. — carbonaria, 1870, Meek and Worthen . 



18. Rhachura? venosa, 1878, Scudder 



19. Hibbertia orbicularis, 1898, gen. et sp. nov 



Carapace — 20. 

 (21. 

 22. 



•3J24 



83 



DEVONIAN. 



Dithyrocaris Belli, 1871, Woodward 



— Kochi, 1864, Ludwig 



breviaculeata, 1864, Ludwig.. 



Kayseri, 1881, Clarke 



? Jaschei, 1856, Ro m er 



25. Mesothyra Oceani, 1888, Hall and Clarke 



26. — Neptuni, 1863, Hall 



127. Choenocaris? Richteriana, 1898, sp. nov. .. 



23. — 



w 



5 



X 



Note.— In our " Seventh Eeport on the Palaeoz. Phyllop.," 1889 (' Brit. Assoc. Rep.,' 1890, 

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

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



