REPORT ON THE ECHINOIDEA. 187 



as in Metalia moderately broad, but scarcely more indented than in BrissojJsis and 

 Hemiaster. It has, like Brissopsis, an anal fascicle, and a closed subanal fasciole indepen- 

 dent of it (PI. XXXV.*" fig. 15). The actinal plastron is very elongated, narrow, extend- 

 ing from the diamond-shaped subanal fasciole nearly to the actiuostome (PI. XXXY." 

 fig. 14). The actinostome is broadly transverse, the ambulacral areas broad, carrying large 

 tufted ambulacral tubes to the edge of the ambitus. The spines of the abactinal surface 

 do not differ in their general aspect from those of Metalia sternalis. The paired ambu- 

 lacral petals are sunken much as in Hemiaster (PI. XXXV.'' fig. 12), the anterior pair are 

 widely separated, placed at right angles to the longitudinal axis ; the posterior pair make 

 but a slight angle with it, are less sunken and are separated by a well-defined rounded ridge. 

 There are four genital pores placed close together. This species seems to be intermediate 

 between Brissus proper and the species which have been separated from it, as Metalia 

 {M. sternalis) and the like. The apex corresponds as in Metalia with the abactinal 

 system (PI. XXXV.'' fig. 13), and is placed nearer the anterior extremity, while it is 

 posterior in Rhinohrissus. 



The only specimens thus far collected show that this species is smaller than Rhinohrissus 

 pyramidalis ; the spines of the abactinal surface are short, of uniform size ; on the actinal 

 side in the lateral posterior ambulacra they are remarkably long, their colour in alcohol is 

 whitish. 



Papeete Harbour, Tahiti ; 20 fathoms. September 28, 1875. 



*Cionohrissus. 

 Cionohrissus, A. Agassiz, 1879, Proc. Am. Acad., vol. xiv. jj. 206. 

 This genus is specially interesting, forming as it does a transition between the Brissina 

 and the Pourtalesise. It has the facies of the former (PI. XXIII. fig. 1), resembling such 

 forms as Brissoj^sis, but having retained somewhat the cylindrical form of the Pourtalesife, 

 and also possessing a rudimentry anal snout (PI. XXIII. figs. 1,4, 7) immediately below 

 the anal system, so characteristic of the latter family, and of which the beak of the sub- 

 anal plastron in Echinocardium and the like is perhaps the first trace, or of which the 

 well-defined area enclosed by the subanal fasciole is the first rudiment, and which in the 

 Pourtalesise takes so extraordinary a development as an anal snout. This characteristic 

 feature of the Pourtalesise of a sul^anal fasciole running round the base of the anal snout 

 (PI. XXIII. fig. 7) is combined in Cionohrissus with a peripetalous fasciole of the Bris- 

 sina (PI. XXIII. figs. 1,6), and ambulacral petals recalling those of Macropneustes from 

 the presence of large primary ambulacral tubercles in the interambulacral areas (PI. 

 XXIII. fig. 6) within the peripetalous fasciole. The groove of the anterior ambulacrum 

 extends to the actinostome (PL XXIII. fig. 9), but is far less marked than in the Pour- 

 talesise, and the actinal surface is not flattened but arched (PI. XXIII. figs. 4, 5), as is 





