4 
THE VOYAGE OF H.M.S. CHALLENGER. 
PAGE 
Description op the Species, &c. — continued. 
MorchelUum, . . . . . . . . . .180 
Sidnyum, . . . . . . . . . . 183 
Polyclinum, . . . . . . . . . .186 
Aplidium, .......... 199 
Amaroudum, . . . ... . . . ... 214 
Psammaplidium, ......... 237 
Genus doubtful, . . . . . . ,. . .251 
Didemnidae, .......... 253 
Didemnum, .......... 260 
Leptoclinum, . . . . . . . . . . 266 
Diplosomidae, . . , . . . . . . . 307 
Diplosomoides, . . . . ... . . 309 
Diplosoma, . . . . . . . . . .313 
Ccelocormidse, .......... 317 
CoeJocormus, . . . . . . . . . . 318 
Polystyelidae, . . . . . . . . . . 322 
Gooddria, .......... 327 
Synstyela, . . . . . . . . . . 341 
Chorizocormus, ......... 345 
Geographical Distribution, . . . . . . . .. . .351 
Bathymetrical Distribution, . . . . . . . . . .371 
Summary and General Remarks, . . . ; . . . .381 
Phylogeny, ........... 387 
Appendices, ............ 401 
Appendix A. Supplementary Report upon the Ascidiae Simplices, . . . .401 
Appendix B. Description of a new species of Psammaplidium, . . . . .419 
Index,. ............ 421 
Explanation op the Plates, . . . . . . .431 
Plates. 
