MUSEUM OF COMPARATIVE ZOOLOGY. 189 



horizontal lines; they are more closely packed and larger on the actinal 

 surface. On the upper part of the test the spines are straight, short, 

 comparatively stout. They are large, slightly curved at the base, and 

 spatulate at the actinal sides The apical part of the anterior interambu- 

 lacrum carries a cluster of longer spines closely packed together, forming a 

 sort of tuft. The spines of the abactinal part of the test resemble at first 

 glance much more those of the regular Echini than those of the Spatan- 

 goids, standing out from the test in all possible directions, and not having 

 a general direction as is usually the case in Spatangoids. The color when 

 alive was of a dark violet. 



This genus differs from Asterostoma only in the absence of actinal am- 

 bulacral furrows and in having a labiate actinostome instead of the pen- 

 tagonal sunken mouth represented in the poorly preserved specimens of 

 Asterostoma. 



100 fathoms off Barbadoes. 



Nacospatangus gracilis A. Ac. (now gen. et sp.) 



Off' Juan Fernandez in 65 fathoms was dredged a small Spatangoid 

 (17 m.m. long), -which will form the type of a subgenus of Spatangus inter- 

 mediate between Maretia and Micraster. It has the high test of Maretia 

 alta, vertex posterior; in the anterior lateral ambulacral petal the abactinal 

 part of the anterior poriferous zone is obliterated, the posterior petals are 

 as in Maretia. The anal extremity of the test resembles that of Spatan- 

 gus proper, but the whole test is covered, as in Micraster, with uniform tu- 

 bercles ; the genus resembles those species of Micraster which have a sub- 

 anal fasciole. In this genus the subanal fasciole is heart-shaped, and 

 sends off an anal branch. The whole surface of the test is covered by 

 silvery-gray short curved spines, somewhat longer on the actinal side, espe- 

 cially towards the posterior extremity of the actinal plastron. 



A very fine series of Ilemiaster Philippii A. Ag. (Loven's Abatns 

 Philippii MS. taken by Kinberg off La Plata). This is extremely inter- 

 esting, as showing how with increasing age the lateral ambulacra, which 

 in young stages (18 mm. long) are slightly depressed, gradually become 

 more and more sunken, til! in specimens measuring 40 mm. in length the 

 lateral ambulacra, especially (lie anterior, are deeply sunken, much as in 

 Tripylus. The peripetalous fasciole does not vary greatly in outline or 

 breadth, and this sjiecies is readily distinguished from II. australis by 

 the short posterior lateral ambulacra, and the narrow peripetalous fasciole. 



