SUPPLEMENTARY NOTES AND OBSERVATIONS. 885 



^^supposition would reduce the fossil to a greater conformity with I. laevis. 

 *' hut it would still be distinct. ^^ I do not undertake to say what may be the 

 characters of undiscovered parts of a fossil, nor do I feel myself competent 

 to found a species upon '* supposed differences." Prof, AV. has constructed a 

 diagram upon a ^^supposed difference" of basal structure, which does not 

 exist in the specimens, so far as they have come under my observation ; 

 and though I have not seen "scores of specimens," all that I have seen 

 are obscurely subangular; and the "bounding lines of the upper and 

 "lower sides of the secondary and tertiary radials" are not always " per- 

 fectly straight," though on the internal casts these lines will necessarily 

 be more nearly direct, since the depression in the middle is an external fea- 

 ture, increased or exaggerated by the thickening of the plate by age ; and the 

 " filling of the sutures" from the inner side will present more nearly 

 straight lines. 



The following diagram, made from a specimen kindly loaned to me by 

 Prof. Marcy, and which I suppose to have been used in the description of 

 I. co7'bis, shows the form and arrangement of the plates of the base and 

 lower parts of the rays, differing in no essential particular from specimens 

 I have identified with /. subangularis* The suture lines of this specimen 

 had been marked with pencil, previous to coming into my hands, and it shows 

 distinctly the series of three radial plates as well as subradials. The speci- 

 men from which my description and figure of /. subangularis was made 

 (Plate 11 (2), fig. 15 of this paper), is from Bridgeport. It preserves the 

 substance of the plates, and is more fit for comparison of external charac- 

 ters than internal casts alone. 



Besides the specimen used for the diagram, there is, in the collection of 

 Prof. Marcy, another one which equally shows the structure of the base, 

 first and second radials. Both specimens are casts of the interiors of the 

 fossil, and show not only the real structure, but the obscurely angular form 

 of the lower part of the body. 



Fig. 1. 



IcnTHTOCRINUS SUBANGULARIS. 



" {h). Lichas imgnax^ W. & M. ; with L. breviceps, Hall. The glabella 

 "is extremely similar to that of L. breviceps, but the pygidium has its axis 



f The basal plates proper of Ichthyocrinus have heretofore been shown by me to be 

 undeveloped externally, or are covered by the summit of the column; and the lower 

 plates, shown on the exterior of the calyx, are properly subradials,_the basals being too 

 minute for representation. 



fAssem. No. 239. ' 49 



