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



ambulacra as in some of the fossil species, but longer than tlie posterior lateral ones. 

 There are two indistinct genital ojDenings in the posterior lateral ambulacra. 



Seen in profile the abactinal outline of the test is nearly parallel to the actiual surface 

 from the posterior extremity to the apical system ; from there, however, it slopes rapidly 

 towards the rounded anterior extremity forming the aml)itus. The tuberculation of the 

 actinal surface is most prominent towards the actinostome in the interambulacral areas, 

 diminishing gradually in size towards the ambitus, where it runs into the granulation of 

 the abactinal surface and sides of the test. 



The beak formed by the jjosterior extremity of the actinal plastron is fully as much 

 developed as in some species of Echinocardium ; the lateral fasciole is sharply defined, 

 and its course well marked as it passes under the anal system about halfway from the 

 ambitus on the posterior extremity. This species recalls more in its outline some of the 

 Tertiary species which have like it a somewhat prominent beak, such as Schizaster 

 archiacii and Schizaster vicinalis, and the like, in spite of the great difierence in the 

 course of the peripetalous fasciole. 



This species is also interesting as it shows how in Schizaster proper the sunken 

 anterior ambulacrum is related on the one side to such genera as Brissus and the like in 

 which the odd anterior ambulacrum is not petaloid, and on the other with genera such as 

 Moira in which the ambulacra are all deeply pouched, while the equal development 

 of the odd anterior petal with the others, is on the contrary a feature characteristic of 

 genera not in the least closely allied to the Schizasteridae such as Spatangus and the like. 

 The sunken petals and the lateral fasciole of this species show its affinities to Tripylus in 

 which we have, however, only the four lateral petals deeply sunken, the odd anterior one, 

 on the contrary, being flush with the test as in Fetor ina and Linthia. This combination 

 of the lateral and perij)etalous fasciole with either more or less sunken lateral and odd 

 ambulacral petals shows unsuspected affinities between such very widely differing 

 genera as Agassizia on the one side, and Moira on the other, which are readily 

 understood when we use as terms of comparison allied forms to either extreme, such as 

 Brissus, Faorina, Brissopsis, Hemiaster, RJtinohrissus, Linthia, and Schizaster on the 

 one side, and Moira, Moiroims, Tripylus, Hemiaster, Faorina, and the like on the 

 other. 



Station 192. September 26, 1874. Lat. 5° 42' S., long. 132° 25' E. ; 129 fathoms; 

 mud. 



The preceding enumeration includes 139 species of Echinids, of which 87 were known 

 before and 52 are new species. The species collected are distributed as follows: — 11 

 Cidaridse (of which 3 are new species), 2 Salenidse (1 new species), 6 Arbaciadse (1 new 

 species), 7 Diadematidte (3 new species), 12 Echinothuridse all of w^hich are new to science, 

 10 Echinometradae (no new species), 16 Temnopleuridfe (3 new species), 11 Triplechinidse 



