350 ECHINOCARD1UM CORDATU.M. 



subanal fasciole is lanceolate, extending to a beak, bounded by a broad fasciole, 

 narrowing rapidly towards tbe actinal surface. The bare ambulacral spaces 

 round the mouth taper rapidly towards the edge of the test. The spines are 

 short, hair-like, except on the oval plastron and the edge of the test, where 

 they are large and spatulate. Color, when alive, yellowish-white. Alcoholic 

 specimens often of a gray color, with pinkish tinge or darker yellowish. 



The specimens of this species collected upon our shores had in the Pre- 

 liminary Report been referred to EcJdnocardmm Kurtzii of Girard, for want 

 of sufficient European material to make a satisfactory comparison of the 

 specimens occurring on both sides of the Atlantic. This comparison has now 

 been made, and shows the identity of the specimens from both sides of the 

 Atlantic. Fragments of this species were collected by Mr. Pourtales. Our 

 American specimens, of which the Museum possesses excellent series, show 

 differences confined almost entirely to a portion of the test, subject to the 

 greatest variation in Spatangoids. These consist in the greater prominence 

 of the posterior abactinal interambulacral ridge, the more circular anal , 

 opening covered bj a slightly larger number of plates than in the European 

 specimens, where they are often larger and fewer in number ; the extremity 

 of the subanal plastron also projects, and is more prominent; — differences 

 which can be found in a large series from any one locality in different 

 individuals. 



Littoral to 85 fathoms. 



Young specimens measuring only G.3 mm in longitudinal diameter have 

 already a labiate mouth, and, as in young Brissopsis, we find very early 

 all the generic features of Echinocardium fully developed, and no one could 

 fail to recognize even in such small specimens the young of E. cordatum. 

 The anterior ambulacrum is as deeply sunk, in proportion to the size of the 

 specimen (PI. XIX. f. 11), as in the adult specimens; the intrapetalous fasciole 

 is fully laid out (PI. XIX. f. 15), though it has a very different outline, being 

 triangular; the lateral ambulacra are totally disconnected as yet; the petals 

 are still linear (PI. XIX. f. 15), and have not yet assumed the characteristic 

 triangular shape of the adult (PL XIX. f. w) ; the anal membrane pro- 

 trudes, somewhat trumpet-shaped, from the anal system ; the subanal 

 fasciole and anal branch are at first united (PI. XIX. f. 14), but as the 

 specimens increase in size, the anal branch separates from it (PI. XIX. f. it)- 

 The actinal plastron is extremely prominent, and in young specimens the - 

 outline of the posterior extremity in profile resembles E. mediterraneum. The 



