140 THE VOYAGE OF H.M.S. CHALLENGER. 



probably as large. It differs from that species, however, in ha\'ing an anal snout (PI. XXII.* 

 figs. 3-5) not so well separated from the test as in Pourtalesia ceratojiyga and other 

 Pourtalesife, l^ut much like that of Pourtalesia lyhiale, only the fasciole extends from the 

 anal surface on the edge of the snout towards the anal opening ; the snout is angular 

 (PL XXII." fig. 3), truncated vertically posteriorly, quite flattened laterally. The few 

 primary spines present near the abactiual system were large, curved, cylindrical ; the 

 smaller secondary ones somewhat club-shaped. There were fragments of the ovaries 

 which seemed long, slender, branching filaments, like those of Pourtalesia laguncula. 



This species is also remarkable for not having, as in other species of the genus, its 

 apical system divided by the encroachment of the posterior lateral ambulacra into a 

 bivium and trivium (PI. XXII. * fig. 6). 



The tuberculation of this species, and the shape of the test, must have been very 

 similar to that of Pourtalesia ceratoi^yga. 



Station 272. September 8, 1875. Lat. 3° 48' S., long. 152° 56' W. ; 2600 fathoms ; 

 bottom temperature, 1'0° C. ; radiolarian ooze. 



*»Spa tagocijstis. 



Sjpatagocystis A. Agassiz, 1879, Proc. Am. Acad., vol. xiv. p. 206. 



Test ovoid, actinal region flattened, the anteriorly prominent actinal keel extending 

 to form an anal snout, the abactinal region of the test regularly arched, the anterior and 

 posterior extremities rounded, the actinal groove sunken. In the apical system, the 

 genital plates connected, placed in the trivium, separated from the bivium by the inter- 

 calated interambulacral plates. 



This genus has, like Pourtalesia proper, a deeply sunken actinal groove. Its 

 outline recalls, however, when seen from aljove, the Holasteridae, and forms the transition 

 between the slightly keeled Holasteridae, and types with more prominent keels extending 

 into a short and small anal snout, which is so highly developed in Pourtalesia proper. 

 The anal groove is sharp, and shows how readily among the Holasterid^ we can pass 

 from a slightly sunken anal system, forming but an unimportant depression on the anal 

 extremity of the test, as in Toxaster and some of the Dysasteridse, to a somewhat more 

 sunken system as in Cardiaster, until we pass on the one side to a well-defined anal 

 groove, as we find it in Metaporhinus, and on the other side to a similarly clearly defined 

 anal groove, forming a deep re-entering angle in the posterior extremity above the small 

 anal snout, a mere beak as it were, formed by the prolongations of the actinal keel 

 beyond the level of the outfine of the test of the posterior extremity. The coronal plates 

 are of a much more uniform size, both in the ambulacral and interamljulacral zones, and 

 assume somewhat the regular arrangement so characteristic of Cysteckinus, in which the 

 Galeritic type of coronal j^lates is still quite prominent. 



In some of the Pourtalesise already, such as Pourtalesia ceratoi^yga, and to a certain 



