Hambach — Revision of the Blastoideae. 63 



Cribroblastus tenuis n. s. 

 Plate v., F;g. 17, 17a. 



Body small, cylindrical, about twice as long as wide. Am- 

 bulacra extending almost over the whole surface of the body. 

 Interambulacra rather convex with a marked crest in the cen- 

 ter. The sutures where the forkpieces meet present a fine 

 furrow as well as the sutures between the fork and deltoid 

 pieces, whose external surface is finely granulated and occupies 

 about one-fifth of the entire length of the body. The rest of 

 the interambulacrum is transversely striated at both sides of 

 the central crest. Genital openings very small, and not con- 

 fluent. Basal part small and flat, visible externally only the 

 thickness of the shell. 



It is easily distinguished from Cribroblastus roemeri and 

 samjpsoni by its more slender form and by the external orna- 

 mentation. 



Geological position and locality : Chouteau limestone, Pet- 

 tis County, Missouri. 



Induced by the sweeping statement of Mr. F. A. Bather, 

 I give the following list, comparing the Blastoids in my 

 collection with those of the British Museum. Accordino- 

 to Mr. Bather's statement, p. x.. Introduction to his Cata- 

 logue, the collection contained then (1899) 1,223 specimens. 

 Quoting his remarks : " These figures speak for themselves. 

 However numerous may be the specimens of Blastoidea in 

 other museums, there can scarcely be any collection so repre- 

 sentative of the class as a whole or as rich in specimens of the 

 highest scientific importance as is that of the British Museum." 

 This is a strong expression, especially since Mr. Bather has not 

 seen all collections. Considering that America contains the 

 bulk of the material, although admitting that the British 

 Museum has the very valuable collections of Gilbertson, I. 

 Rofe and L. G. de Koninck of unique specimens, I venture 

 to say that our American material is on the whole better pre- 

 served than that found in Europe, and being confident that the 

 American collectors did not send their best specimens across 



