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



OfFCebu, 100 fathoms. 



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

 mud. 



'''Asthenosoma coriaceum (PI. XVIL* figs. 5-7). 



Asthenosoma coriacea, A. Agassiz, 1879, Proc. Am. Acad., vol. xiv. p. 201. 

 This is a large species allied to Asthenosoma gruhii in having an extremely thick 

 leathery cuticle, but readily distinguished from it by the greater height of the coronal 

 plates ; in specimens of the same size there are more than twice as many plates as on the 

 abactinal surface of Asthenosoma gruhii. The plates of the abactinal surface carry but 

 fcAV primary spines limited to the neighbourhood of the ambitus ; while on the actinal 

 surface the plates bear over a great part of the floor, long comparatively stout hollow 

 primary spines but slightly curved and very slightly flaring, resembling more nearly the 

 primary actinal sj)ines of Phormosoma than the characteristic flaring trumpet-shaped 

 spines of Asthenosoma. The abactinal surftice is nearly bare; it carries but few primaries 

 near the ambitus, and small, short, sharp secondaries and miliaries confined mainly to 

 the outer edges of the ambuhicral and interambulacral zones. With this exception the 

 general arrangement of the tubercles both in the ambulacral and interambulacral areas 

 resembles that of Asthenosoma tessellatum ; the coronal plates are also more prominently 

 pitted (PL XVIL* figs. 6, 7), and towards the abactinal system, where the plates are very 

 narrow, their presence is indicated by angular rows of pits following the course of the 

 coronal plates (PL XVII. * fig. 7). It is quite possible, as I have stated in the pre- 

 liminary Report of the Challenger Echini (Proc. Am. Acad., 1879, vol. xiv. p. 201), that 

 this may be the adult of Asthenosoma tessellatum, yet from the identity abeady clearly 

 apparent in specimens difiering far more in size in other species of the genus, both in 

 Asthenosoma jieUucidum and in Asthenosoma gruhii, I am inclined to keep it distinct 

 for the present, as in the sjDecimens of Asthenosoma tessellatum, measuring 140 mm., 

 and in one of Asthenosoma coriaceum, 220 mm. in diameter, there is only a diflerence of 

 a few plates in the number of coronal plates, while we might expect, judging from their 

 size, a greater difierence in the number. 



Station 173. July 24, 1874. Lat. 19° 10' S. ; long. 179° 40' E. ; 315 to 310 

 fathoms ; coral. 



Station 172. July 22, 1874. Ofi" Nukualofa, Tougatabu ; 18 and 240 fathoms; 

 coral. 



''' Asthenosoma tessellatum (PL XII.^ figs. 14, 15; PL XIX.^ fig. 1; PI. XIX."). 



Asthenosoma tessellata, A. Agassiz, 1879, Proc. Am. Acad., vol xiv. p. 201. 

 Only a single specimen of this species was collected ; it is of a dark chocolate colour. 



