52 HAWAIIAN AND OTHER PACIFIC ECHINI. 



The Genera and Species of Salenid^. 



This well-marked family contains ten apparently valid and clearly recog- 

 nizable genera, of which, however, only two contain recent species. These 

 genera are distinguished from each other by the position of the suranal plate, 

 the condition of the tubercles (i. e. whether perforate or not), the presence 

 or absence of compound ambulacral plates abactinally, the presence or ab- 

 sence of sphjBridial pits, and the ornamentation of the abactinal system. A 

 convenient grouping of the genera according to these characters may be 

 made as follows: 



Suranal plate axial and anterior, in contact with only four genital plates. 

 Primary interambulacral tubercles perforate. 



Ambulacra broad, straight, or little flexuous, with perforate primary tubercles. 

 Ambulacral plates above ambitus, compound. 



Compound ambulacral plates made up of 3 plates . . . Acrosalenia. 

 Compound ambulacral plates made up of 2 plates . . . Plesiosalenia. 



Ambulacral plates above ambitus simple primaries Perisaleiiia. 



Ambulacra narrow, flexuous, with only imperforate small tubercles 



or granules Pseudosalenia, 



Primary interambulacral tubercles, imperforate. 



Large pits (for sphaeridia ?) present in actinal, ambulacral plates . Goniophorus. 



No such pits present Peltastes. 



Suranal plate not axial, but in contact with all five genital plates. 



Primary interambulacral tubercles perforate Heterosalenia. 



Primary interambulacral tubercles imperforate. 



Ambulacral plates compound, made up of 2 plates Salenia. 



Ambulacral plates, except one or two at peristome, simple prima- 

 ries only. 

 Ambulacral tubercles numerous (more than 20) ; abactinal 

 system with plates distinctly separated by grooves or pits 



and not covered with tubercles Salenidia. 



Ambulacral tubercles usually less than 15, rarely more than 

 20 ; abactinal system with plates not distinctly separated 

 and covered with small, rough tubercles Salenocidaris. 



The genera Hyposalenia Desor and Poropeltaris (or Poropeltis) Quenstedt 

 (1875, Petr. Deutsch. : Ech. p. 242) are simply synonyms of Peltastes, while 

 Trisalenia Lambert appears to have been based on a misconception, and 

 Eosalenia Savin is not one of the Salenid^. Pomel's genera Bathysalenia 

 and Pleurosalenia are not distinguishable from Salenidia and Salenocidaris. 



