258 SALENIA. 



upon a more or less distinct mamelon. The structural features of the buccal 

 membrane of Cidaridae, of the teeth and of the poriferous zone, appear to 

 entitle them to a higher rank than that of a family, in the suborder of Echi- 

 noids, intermediate between the Palaechinidae and Eclnnidae proper. 



SALENIDAE. 

 Subfamily Salenidae Agass. 1838. Mon. Ech. Salunies. (emend.) 



SALENIA. 



Saleuia Gray, 1825. Ann. PbiL 



Small Echini, remarkable for the extraordinary development of the abac- 

 tinal system, the connection of one (large subanal plate) of the anal plates 

 with the genital plates, the other anal plates very small, the sutures of the 

 abactinal plates more or less pitted, the madreporic body quite indistinct, 

 [nterambulacral areas broad, coronal plates few in number, tubercles in ten 

 principal rows, imperforate, distinctly crenulated, median interambulacral 

 occupied by vertical rows of small secondaries, carrying different kinds of 

 spines (papilliform) from those of the primaries, the abactinal part of am- 

 bulacra having similar spines. Primary spines large, of various shapes. 

 Poriferous zones narrow, pores arranged in single vertical pairs. Buccal 

 membrane imbricated, but ambulacra not extending through the buccal 

 plates, as in Cidaridae and some Diadematidae. 



The structure of the abactinal system in young Echini explains most unex- 

 pectedly the homology of the subanal plate of Salenidae, which has been such 

 a puzzle to Echinologists. In the lirst place, I must reiterate that the posi- 

 tion of the anal system within the abactinal system is not one which can 

 be defined geometrically by any axis we can draw, nor does it hold any 

 organic connection with the general structure of Echini; the madreporic 

 body alone, in Echini proper, giving us the key to the position of an axis 

 which is most intimately connected with the structure of tin- Sea-urchin. The 

 genital plates are not equally developed : in some genera the ocular plates 

 occupy an intermediate position between genital plates of apparently the same 

 size; but in others the posterior genital plates are somewhat less developed, 

 and the ocular plates are thus placed in direct contact with the anal system, 



