LECANOCRINIDAE 1 75 



The genus embraces two forms from different horizons in the Niagaran Group which 

 diverge rather widely in superficial appearance, both being intermediate as to family charac- 

 ters, but concurring in the most essential of these characters. The first belongs to a numer- 

 ously represented type from the Rochester shales at Lockport, New York, heretofore 

 described under Lecanocrinus, from which it must be removed on account of the lack of 

 lateral contact of the rays, and the presence in varying degrees of a perisomic integument 

 between them. In this form the anal tube is but slightly developed, but its origin is indicated 

 by a curious modification of the anal plate, which for a part or the whole of its length is out- 

 wardly curved into a strong longitudinal ridge of the form and size of the tube plates which 

 follow it. These are rarely more than two or three in number, and in many specimens where 

 the posterior rays lie close together they are not visible. In many specimens also the inter- 

 brachial perisome cannot be seen, owing to the narrowness of the areas and to the fact that 

 the perisome is deeply imbedded. There is a marked gradation in this feature among the 

 Lockport specimens, some having the areas fairly wide and the perisome readily distin- 

 guished, leading up to the later Tennessee form in which it is very conspicuous. The New 

 York form is represented by three species, all from the same horizon and locality, which may 

 be only variants of a single prolific type. 



The genus culminated in a fine species recently discovered from the later Brownsport 

 limestone of Tennessee, which I have taken as the type because in it all the generic characters 

 are most fully developed. The interbrachial areas have become very wide, filled with strong 

 perisome like those of Pycnosaccus, and with the increased space thus afforded the anal tube 

 has become a prominent object. In both forms there is an evident tendency to modification 

 of the anal structures in the direction of the Taxocrinidae, and as in the cases of Meristocrinus 

 and Synerocrinus the genus stands near the border line. There is also in both a tendency to 

 irregularity in the number of primibrachs, but this is only sporadic, the normal number gener- 

 ally holding good. In the secundibrachs, however, there is a constant difference between the 

 New York and Tennessee forms. 



The four species may be arranged as follows : 



The Species of Asaphoceinus 



I. Anal tube slightly developed ; anal x curved into longitudinal ridge. 

 IIBr 3 or more. 



Calyx not differentiated, low and rounded. 



iBr areas narrow, with little space for perisome. 



RR smaller than BB. IBr half as high as RR A. ornatns. 



Calyx not differentiated, more or less turbinate. 

 iBr areas of medium width, exposing perisome. 



RR smaller than BB. IBr about half as high as RR A. excavatus. 



iBr areas narrow. 



RR larger than BB. IBr very low A. incisus. 



II. Anal tube long and well-developed. 

 IIBr 2 (or i). 



Calyx well differentiated. 



iBr areas wide, filled with strong perisome. 



RR much larger than BB A. bassleri. 



