202 PROCEEDINGS OP THE AMERICAN ACADEMY 



from the abactinal side, and the few long, large, dark violet primary 

 spines of this surface, with similarly colored short, fine secondary and 

 miliary spines standing out in bold contrast to the light test, and by the 

 large size of the anal system and of the genital openings on the actinal 

 side. The primary tubercles of the actinal side carry large spines 

 tipped with white cup-shaped appendages, performing for this group 

 the same functions as a similar tip on the spines of the actinal side 

 of the Arbaciadre. The secondary and miliary spines similar to those of 

 the abactinal side. One specimen in the collection differs from the 

 majority of the others in having the test and spine of a uniform 

 yellowish-pink color. Station 200, 255 fathoms; Station 205, 1,050 

 fathoms ; Station 332, 245 fathoms. 



Phormosoma tenuis, A. Ag., nov. sp. 



Closely allied to Phormosoma uranus, W. Th., from which it dif- 

 fers mainly in having larger and more numerous primary tubercles, 

 especially on the actinal side, while on the abactinal side the small 

 number of miliaries occurring in this species give it a very different 

 facies. The coronal plates are more numerous in P. uranus than in 

 specimens of the same size of this species, and the abactinal system is 

 also proportionally smaller in P. tenuis, and the anal system made up 

 of larger plates. — Station 274, 2,750 fathoms ; Station 237, 1,875 

 fathoms. 



Prionechinus sagittiger, A. Ag., nov. gen. & sp. 



The apical system of this genus is similar to that of Salmacidae. 

 Single row of plates of pores on each side of median ambulacral line. 

 Actinal membrane covered by plates. Spines serrated, somewhat flat- 

 tened, radically different from those of any other genus of Triplechinidse. 

 As is well known, the serrations of the spines of young Echini proper 

 disappear with age, and it is only among the Cidaridre, Salenidae, and 

 the like, that we find spines greatly differing in allied genera or spe- 

 cies, the spines of the Echinidoe proper being remarkable for their 

 uniformity. Unfortunately only indifferently preserved specimens of 

 this interesting genus were collected, and they are probably not fully 

 grown, as the large anal system is still covered by a few large plates, 

 as in all young Echini. Genital plates of uniform size ; ocular plates 

 notched in apex, excluded from anal system. — Station 164, 950 

 fathoms ; Station 218, 1,070 fathoms. 



