REPORT ON THE ECHINOIDEA. 163 



green specimens had a higher test than the violet specimens, which were all much flatter ; 

 otherwise no specific differences were noticed. The plates of the anal system all carry a 

 small secondary tul:)ercle, and the anal opening extends into a short conical i^rojection 

 (PI. XXX v." fig. 3). The actinostome is elongated, transverse, with a well-marked raised 

 posterior labial edge ; the actinal membrane is strengthened l^y a number of small plates 

 arranged in irregular concentric rows ; the structure of the actinal plastron is well shown 

 in Plate XXXI. fig. 1. The shape of the test varies considerably in the few specimens 

 collected ; the youngest specimens (PI. XXXI. figs. 20-22) show when seen from above 

 an angular outline, with a comparatively conical outline when seen in profile, and rather 

 distant spines. In a somewhat older specimen the outline seen from above is nearly 

 circular (PI. XXXI. figs. 16, 17), the apex with the apical system is posterior (PI. XXXI. 

 fig. 16). When seen in profile it is high (PL XXXI. fig. 19), the test sloping gradually 

 towards the anterior extremity and more suddenly towards the posterior extremity; the anal 

 system is placed high above the ambitus (PI. XXXI. fig. 18). These young specimens of 

 Genicopatagus would readily pass for the young of a Paleopneustes (allied to the Florida 

 species) were it not for the different structure of the apical system, from their general 

 outline and from the total absence of any fasciole. The more ordinary outline of the test 

 when seen in profile is represented in Plate XXXI. fig. 14, which shows a much more 

 flattened test and a rudimentary, rounded anal keel below the anal system (PL XXXI. 

 fig. 15). The anal system is also, in this older specimen, nearer the ambitus than in 

 the specimen of Plate XXXI. figs. 16-19 ; while in the youngest specimens it is placed 

 immediately above the ambitus (PL XXXI. fig. 20). The outline of these older specimens 

 seen from above does not differ materially from that of the younger more conical speci- 

 mens ; the anal extremity is somewhat more pointed (PL XXXI. figs. 12, 13). 



Station 157. March 3, 1874. Lat 53' 55' S., long. 108° 35' E. ; 1950 fathoms; 

 diatom ooze. 



Homolampas. 



lAssonotus, A. Agassiz, 1869, Bull. Mus. Comp. Zool., vol i. {non Sclionh). 

 Homolampas, A. Agassiz, 1872, Eevis. Ech., part 1, p. 137. 



I have already alluded in the Revision of the Echini to the similarity in structure of 

 the abactinal ambulacral region of Homolampas to that of Cardiaster and Holaster. 

 In the large species {Holaster fulva) discovered by the Challenger, the close afiinity 

 of the genera is still more evident. Homolamp)as has very rudimentary petaloid 

 ambulacra; it has a peripetalous fasciole which corresponds to the lateral fasciole 

 of Cardiaster, having, like it, nothing exactly limiting the ambulacra until they 

 nearly reach the ambitus, where its lateral fasciole would occupy homologically 

 the position of a peripetalous fasciole, and pass below the anal system, though in 

 reality it is a lateral fasciole as we understand it among the recent genera. The next 



