HOMOLAMPAS. 347 



Radiating from the apex towards the mouth, and extending along the 

 abactinal plastron {PI. XVIII. f. 8), there are masses of pigment cells 

 forming lines of dark violet spots, also a similar series of spots round the 

 extremity of the anal prolongation of the test, particularly marked on the 

 edge of the pit leading to the anal opening. The test is extremely thin, 

 transparent, of a bluish-gray color in alcohol, in this specimen, as well as 

 in a still younger specimen collected by the Porcupine Expedition. In 

 an older specimen, also dredged by the Porcupine Expedition, the test 

 was much stouter. From the above description it is evident that Infu- 

 laster and the Ananchytidae must have had a structure allied to that of 

 Pourtalesia, and are embryonic Spatangoids, still retaining some features 

 of Clypeastroids, while the features characteristic of young Spatangoids are 

 prominently developed. 



A single specimen of this interesting genus was dredged at a depth of 349 fathoms. 



HOMOLAMPAS. 



Homolampas A. Agass. 1872. Rev. Echin. Pt. I. 



This genus is intermediate between Cardiaster and Holaster. It has, like 

 those genera, ambulacra flush with the test, but, unlike Holaster, has a well- 

 developed anal and subanal fasciole, while it wants the lateral fasciole of 

 Cardiaster. The ambulacral pores form no petals ; they extend as simple 

 pores between the ambulacral plates from the phyllodes to the apex. The 

 actinal surface is flat ; the actinostome is pentagonal, not bilabial, with well- 

 developed phyllodes, but without trace of bourrelets, — a strong connecting 

 link between the Cassidulidae and Spatangoids proper. The compactness of 

 the apical system of this genus is in marked contrast with its structure in 

 allied genera, such as Cardiaster and Holaster. 



The general outline of the test resembles Maretia, but is somewhat more 

 elongate. It is closely allied to Platybrissus, but the presence of a subanal 

 fasciole, as well as a slight anterior groove, readily distinguish the two 

 genera, in addition to the presence of a rudimentary rosette in Platybrissus, 

 wanting in this genus. 



