Hambach — Revision of the Blastoideae. 33 



of classification is to be found in the diagnosis of Nucleoblas- 

 tidae, Etheridge and Carpenter. This family is divided into 

 Sub-faniilv A. Elaeacrinidae and Sub-family B. Scbizoblas- 

 tidae. The only peculiarities common to both are the elliptical or 

 ovoidal form of the body and the extremely short fork-pieces, 

 which latter fact is not mentioned in their diag-nosis. Elaea- 

 annus has its posterior deltoid divided and an elongated piece 

 inserted, which is never the case in SchizoblastuH. Moreover 

 the center of the summit is firmly closed by pieces of a uni- 

 form shape and position in Elaeaci'inus, which is not the case 

 in Schizohlastus where the center is open, or closed only by 

 the ambulacral integument. 



Nicholson and Lydekker's description of this family, which 

 is accompanied by two figures, is still more confused, reading as 

 follows : — 



"Family III. Nucleoblastidae. Calyx usually globular 

 or ovoidal with flattened or concave base and linear ambu- 

 lacra. Spiracles distinctly double, and chiefly formed by 

 the opposition of notches in the lancet plates and deltoids. 

 This family includes Elaeacrinus (with an anal plate) and 

 Schizohlastus, Fig. 332 c and d, Crypfoblastus and Acento- 

 tremites (without an anal plate)." 



PROPOSED CLASSIFICATION. 



The classification here offered is based mainly on the con- 

 struction of the summit openings, because they exhibit a 

 uniformity in structure, remaining always the same in their 

 respective genera — a fact which must be of great value for 

 classification. Next the development of the deltoids is con- 

 sidered, also the aspect of the outer surface (whether smooth 

 or spiny). Whereas the general size and shape of the body, 

 whether globose, pyriform, ovoidal, conical or clavate, 

 depends upon the variations in the form of the parts which 

 construct the body, and whereas the relations of these parts 

 to each other remain the same throughout the whole class, 

 the difference can be only specific and not generic. Nor can 

 we attribute any more than specific value to the hydrospiric 

 tubes, or plications, on account of the variability often 



