1886.] NATURAL SCIENCES OF PHILADELPHIA. 141 



and as the plates were arranged very differentl}'' from those of 

 other genera, we suspected that the type specimen was a mal- 

 formed or recuperated Gyathocrinus. This view, however, must 

 be given up, since other specimens have been found which show 

 the plates under similar conditions. Mr. Walter R. Billings 

 informed us, in 1880, of the discovery of two more specimens in 

 which the azygous plates were arranged as in E. Billings' type. 

 These specimens were afterwards noticed by him in the Trans- 

 actions of the Ottawa Field Naturalist's Club of 1881, p. 35. 



Carabocrinus was described by E. Billings using our termin- 

 ology to be constructed of five underbasals, four of them penta- 

 gonal, the fifth hexagonal ; five basals, three of them hexagonal, 

 one heptagonal and one pentagonal, the latter smaller than the 

 others ; of five radials ; three azygous plates, one of them sup- 

 ported upon the hexagonal underbasal, a second upon the small 

 pentagonal basal, the third between two radials. Consulting the 

 generic diagram, Decade iv, p. 30, we find that the smull, penta- 

 gonal basal (subradial plate of Billings) has scarcely half the 

 size of the other basals, and the first azygous plate is placed at 

 its left side, contrary to all other Cyathocrinidte. This structure 

 seemed to us so improbable that before accepting it we applied 

 to Prof. Whiteaves of the Canada Survey Museum for the type 

 specimen. We now found that in Billings' diagram the plate in 

 question is represented considerably larger than it is in the 

 specimen, the so-called " azygous plate," to the left of the former, 

 smaller, that the basals at their lower sides form in the specimen 

 a much more obtuse angle, almost a straight line, and that the 

 underbasals are comparatively smaller. 



From our diagram it will be seen, that the second or basal ring 

 really consists of six plates, four of them equal, the fifth one nearly 

 as high but somewhat narrower, the sixth subquadrangular, small, 

 not more than half the size of the former. That the laiter piece 

 which is united with the az^-gous plate by a horizontal suture is 

 a basal subradial of Billings seems to us exceedingly doubtful, 

 the more as the adjoining plate meets all the requirements of a 

 basal. This plate, which Billings called the first azygous piece, 

 and which we take to be the posterior basal in conformit}^ with 

 other Cyathocrinidge, has an azygous plate at its right side, 

 and this supports with its right upper sloping side a special anal 

 plate. The small plate within the basal ring, which is only known 



