202 PANAMIC DEEP SEA ECHINI. 



Seen in profile (PI. 107, fig- #), the apex is posterior. Fig. 288, nearer the 

 transverse fasciole. Anteriorly the test slopes somewhat more gradually 

 towards the ambitus than towards the posterior extremity, which is slightly 

 indented at the anal system, the anus is placed almost half-way from the 

 ambitus to the vertex. 



As in Agassizia, there is a central apical plate, Fig. 289, composed of the 

 four ankylosed genitals. The genital pores are not as yet developed (PI. 

 106, figs. J, 4), and the madreporic body can barely be detected from the 

 exterior (PI. 106, fig. 2). Seen from the interior the base of the stone 

 canal projects prominently from the level of the central plates. 



The ocular plates are large, irregularly hexagonal, they abut against 

 the central genital plate, except the left anterior, which is separated from 

 it by the intercalation of a row of lateral interambulacral plates (PI. 106, 

 figs. 2, 4). 



The primary actinal interambulacral plates and those of the odd and 

 of the posterior interambulacra are nearly of the same size ; the labium is 

 somewhat larger (PI. 106, fig. l). 



The tentacles of the odd anterior ambulacrum are large with prominent 

 disks (PI. 107, fig. 6). 



Station 2769, ''Albatross" Exp. New York to San Francisco, off Cape 

 Dos Bahias, in 51 fathoms. Lat. 45° 22' S. ; Long. 64 20' W 



Nacospatangus A. Ag. 

 Nacospatangus gracilis A. Ag. 



Nacospatangus gracilis A. Ag., Bull. M. C. Z. 18~.">, III, p. 189. 



Nacospatangus gracilis A. Ag., " Hassler " Exped. Echini, p. 18, 111. Cat. M. C. Z. 1874, 



No. VIII. 



Plate 98. 



Although I have given photographic figures of Nacospatangus, 1 yet 

 as they do not bring out sufficiently clearly the important characters of 

 this interesting genus, I have given on Plate 98 additional figures which 

 will show more in detail the specific and generic characters described in 

 the "Hassler" Echini, and bring out its distant relationship to Agassizia 

 and Spatagodesma. 



1 111. Cat. M. C. Z. No. VIII, PI. II, figs. 3-5. 



