294 PROCEEDINGS OF THE ACADEMY OP [1885. 



perisomic plates, and we cannot understand how Carpenter can 

 admit interradials in Apiocrinus roissyanus, and not in Apio- 

 crinus Meriani (De Loriol, Pal. Franc, tome xi, PI. 40), Apio- 

 crinus Ralhieri (Ibid., PI. 50) and Apiocrinus murchisonianus 

 (Ibid., PI. 53). But it is still more remarkable that in Apiocrinus 

 roissyanus Carpenter considers only the first row, and not the 

 succeeding ones also, as calyx plates. The latter are equally 

 solid, suturally connected, and rest like the first plate, between 

 the primary radials. 



In our opinion Carpenter lays too much stress upon the 

 asymmetry of the calyx in the Palseocrinoidea, which he attributes 

 to the intercalation of an anal plate. If the asymmetry of the 

 basals was due to that cause only, genera such as Eucalypto- 

 crinus, Coccocrinus, Mycocrinus, Dolatocrinus and Corymbo- 

 crinus, which have no anal plates in the calyx, should have very 

 regular basals, while in fact Eucalyptocrinus has the same basal 

 arrangement as Melocrinus, Dolatocrinus as Hexacrinus, Corymbo- 

 crinus as Abacocrinus, the last named of which all possess anal 

 plates. It is also well known that in Platycrinus and the Blas- 

 toidea, and all other genera with three unequal plates in the basal 

 ring, the smaller plate is always located to one side, not pos- 

 teriorly, and it is difficult to understand how in Haplocrinus the 

 asymmetry of the calyx could be attributed to an anal plate, or 

 to the anal opening, when the latter penetrates the very top of 

 the so-called "orals." We admit that the dorsal cup is more 

 frequently asymmetrical in Palreocrinoidea than in Neocrinoidea, 

 but exceptions are so numerous that we cannot attach to this 

 point the importance that Carpenter does, who considered the 

 s} T mmetry, or want of symmetry, to be the best distinction 

 between the two groups. We believe the condition of the mouth, 

 and that of the oral surface generally, is of much greater import- 

 ance, and proves to be a more constant character than any of 

 those to which attention has been directed. Carpenter thinks 

 Coccocrinus forms an exception to this rule, which he regards to 

 be in the condition of the Xeocrinoid genus Holopus, and that 

 consequently its mouth was exposed. If this were true, we should 

 not hesitate a moment to refer that genus to the Neocrinoidea, 

 as nothing would be left to make it a Paloeocrinoid, not even the 

 asymmetry. 



Carpenter denies that interradials are present as a rule in 



