360 DR MURRAY ON THE DEEP AND SHALLOW-WATER MARINE FAUNA 



Pourtalesia^ carinata, Agassiz. 

 ,, ceratopyga, Agassiz. 



* ., hispida, Agassiz. 



2)hiali\ Wyville Thomson. 

 Schizaster'- moseleyi, Agassiz. 

 * S'patagocystis challengeri, Agassiz. 

 Urechinus naresianus, Agassiz. 



HOLOTHURIOIDEA : 



*Achlyonice lactea, Tlieel. 

 BeutJiodytes sanguinolenta, Theel, var. marginata, Tli(^el. 



,, sordida, Theel. 



Cucumaria abysso7^m, Theel. 



,, „ var. hyalina, Theel. 



*El'pidia amhigua, Theel. 

 ,, glacial is, Theel. 



* ,, incerta, Th(^el. 



* ,, purpurea, Theel. 



* „ willemoesi, Th^el. 



Holothuria thomsoni,' Theel, var. hyalina, Th^el. 

 Kolga nana, Theel. 

 Lcvtmogone ivyville-tliomsoni , Tht^el. 

 Oneirophanta mutahilis, Theel. 

 *Peniagone affinis, Th^el. 



* ,, atrox, Theel. 



* ,, challengeri, Th6el. 



' In the genus Pourtalesia proper, as I have retained it here, there are two groups of species readily distinguished 

 from the character of the test ; these I was at first inclined to separate into distinct sub-genera on comparing such extreme 

 forms as Pourtalesia miranda, laguncuhi, and phiale with such forms as Pourtalesia ceratopyga and rosea. The former 

 group is distinguished by the extreme tenuity, almost transparency, of the test and its more or less bottle-shaped out- 

 line, while the latter group contains species with a flattened test, a triangular outline from above, and a comparatively 

 thickened test. — (Agassiz, Zool. Chall. Exp., part 9, pp. 132-3.) 



- The limits which have lieen assigned to the genera closely allied to Schizadcr are very unsatisfactory, and the 

 generic characters by which different species are assigned to these genera or sub-genera pass so gradually one into the 

 other, not merely among the recent species, but especially when we come to include the fossil species, that tlie task of 

 properly limiting them appears hopeless, although these characters are convenient as sub-divisions according to which 

 we may associate groups of species. — (Agassiz, Zool. Chall. Exp., part 9, p. 200.) 



5 The three species above mentioned, viz., Holothuria lactea, Holothuria thomsoni, and Holothuria murrayi, form a 

 group by themselves among the numerous representatives of the genus Holothuria, and it is very probable that they 

 may be properly placed in a new genus, or, at least, in a sub-genus. Indeed, Holothuria thomsoni difl'ers so strikingly 

 from all forms hitherto known that I should not hesitate to refer it to a new genus if I had not had the opportunity 

 of examining the two other forms, which evidently form a transition to the true Holothuricc. Holothuria thomsoni is 

 distinguished by twelve tentacles, and its variety by fifteen, numbers of tentacles hitherto unknown in any species of 

 Holothuria. That which seems to be common to the three species above mentioned and their varieties is, firstly, the 

 conformation of the calcareous deposits, and secondly, the peculiarity that the pedicels of the two lateral ventral 

 ambulacra either form a simple distinct row, or ihat, if they are more numerous and crowded, some of them are larger 

 and more or less distinctly arranged in a row along each side of the body. — (Tn^EL, Zool. Chall. Exp., part 38, p. 187.) 



