POURTALESIIDAE. 125 



fossil forms and is accordingly placed in the Echinocorythidae with them. 

 There is only a single species known, three specimens of which were taken by 

 the Siboga at two widely separated stations in the East Indies at depths of 

 290-460 fms. 



CALYMNIDAE Mortensen. 



This family was proposed for the single genus Calymne. It differs from 

 the proceeding only in having all the ambulacral pores simple. 



Calymne. 



Wyville Thomson, 1877. Voy. Challenger. The Atlantic, 1, p. 397. 

 Type, Calymne relicta Wyville Thomson, 1877. Loc. cit. 



This genus and species is based on a single fragmentary specimen col- 

 lected by the Challenger near the Azores Islands at the extraordinary depth of 

 2650 fms. Until more material is secured, the genus is most easily provided 

 for by giving it a family of its own. 



POURTALESIIDAE LovSn. 



This is undoubtedly the most remarkable and the most specialized family 

 of Echini. As it has been very extensively studied by Lov6n, A. Agassiz, and 

 Mortensen, there is very little to add to our knowledge of it, particularly as 

 the only material available, not already worked over by Mr. Agassiz, consists 

 of a single species of Pourtalesia. The pedicellariae in the family are notable 

 and oftentimes characteristic. The ophicephalous in particular are of a type 

 peculiar to this family and quite unlike those occurring among other Echini. 

 The various forms have been fully described and figured by Mortensen. The 

 following key to the genera is compiled from Mortensen's work, and much of 

 the material in the keys to species is from the same source. 



Key to the Genera of Pourtalesiidae. 



No subanal rostrum present. 



Tube-feet near mouth penicillate; a fasciole present on oral surface; test more 



or less hemispheric or ovoid Sternopatagus. 



Tube-feet near mouth not modified; no fascioles; test not hemispheric or ovoid. 



Apical system compact; test widest anteriorly Echinocrcpis. 



Apical system disjunct; test not widest anteriorly Cystocrepis. 



