322 ECHINODERMS OF THE BRITISH ISLES 



[Fam. Pal^opneustid^] 



The various deep-sea genera united into this family agree with 

 the Spatangoids proper in having the peristome transversely 

 elongate and the first plate of the posterior interambulacrum 

 modified into a more or less prominent labrum, but differ from 

 the other Spatangoids in the ambulacra being simple on the 

 dorsal side, not petaloid widened, or, when slightly petaloid in 

 larger specimens, not sunk.^ 



Two genera are known from the N.E. Atlantic and may be 

 expected to occur also in the British seas, namely Palceotropus 

 Loven and Peripatagus Koehler. Of the former, one species, 

 Palceotropus Josephince Loven (Syn. Palceobrissus Hilgardi A. 

 Agassiz ; Palceotropus hirondellei Koehler ),2 has been found in 

 the Bay of Biscay and off the Azores (" Josefina ", '' Hirondelle ", 

 " Princesse Alice "), in depths of 500-1600 m. ; also found in the 

 West Indies. Of Peripatagus only a single species is known, 

 namely P. cinctus Koehler, found off the Azores, 880-1494 m. 

 C' Hirondelle ", "Princesse Alice"). The two forms are thus 

 distinguished : 



A subanal fascicle present (obliterating in the larger specimens) ; 

 no marginal fasciole .... Palceotropus Loven 

 No subanal fasciole ; a marginal fasciole present 



Peripatagus Koehler 



Detailed descriptions and figures of these two forms are given 

 by Koehler {"Monaco,'' Fasc, xii., p. 29, Pis. V., VI.; Fasc. 

 xxxiv., p. 248, PI. XXXI.), A. Agassiz {''Blake " Echini,^^. 53, 56, 

 Pis. XXIII. , XXIV.), as also by Loven {Etudes sur les Echinoidees, 

 p. 17, PI. XIII.). 



I. Family Hemiasterid.^ 



Ambulacra on upper side of test petaloid widened and more 

 or less sunk ; first plate of posterior interambulacrum developed 

 into a promiuent lip partly covering the mouth and the trans- 

 versely elongate peristome. No closed subanal fasciole. 



Two genera represented in the British seas ; a third genus, 



^ The family is not well defined, but as far as the N.E. Atlantic forms 

 are concerned there is no trouble in recognising them as different from the 

 true Spatangoids (the families Hemiasteridse and Spatangidae). 



- H. L. Clark is responsible for making Palceobrissus Hilgardi and 

 PalfjBotropus hirondellei synonyms of Palceotropus Josephince ; the present 

 author has had no opportunity for a closer study of these forms. 



