LECANOCRINIDAE \2J 



Homalocrinus, Calpiocrinus, and Anisocrinus; but it is broadly separated from all these by 

 the absence of interbrachial structures. 



Hall's generic diagnosis of Lecanocrinus 1 contained chiefly what we now regard as 

 family characters, but he noted the presence of an " interscapular " (anal) plate. With his 

 usual strong grasp of fundamental relationships in fossils, even at that early day when these 

 matters were by no means understood as they are now, he was struck by what he called " a 

 very interesting analogy " between this form and Ichthyocrinus. He showed how, if the 

 " three minute plates " at the base of the latter should be more fully developed, " we should 

 have the pelvis of Lecanocrinus" ; and a like development of the five "triangular pelvic 

 plates " of Ichthyocrinus would produce the " costal plates of Lecanocrinus." And he pro- 

 ceeded to show a still further analogy between the two genera by reference to a diagram 

 {op. cit., pi. 45, fig. 2) showing a small intercalated plate, which he compared to the " inter- 

 costal plate" (radianal) which he had described in Lecanocrinus. This diagram, however, 

 simply shows an exceptional case, of which I have seen two or three, where an accidental 

 interbrachial plate appears ; it has no place in the structure of Ichthyocrinus. 



Schultze 2 discussed the genus in connection with his species from the Devonian, and 

 proposed to extend its geological range by including the two species described by De Koninck 

 under Mespilocrinits, which he declared " undoubtedly belong to Lecanocrinus." The im- 

 portance of the radianal as distinguishing these two genera had not then been recognized, but 

 Schultze did not overlook the plate, which he called a second smaller interradial, saying that, 

 " according as it is more or less developed is to be reckoned either with the radial or para- 

 basal ring." 



Bather 3 correctly diagnosed the genus, and placed it in a family with Ichthyocrinus, 

 Clidochirus, Mespilocrhms, Pycnosaccus and Nipterocrinus, which in regard to the last three 

 agrees with the present arrangement. 



Angelin's Cyrtidocrinus, 4, said by him to have four " basalia " (i. e., infrabasals), and for 

 that reason referred to a different family, is a synonym of this genus. It was founded upon 

 incorrect observation, as Liljevall's figures of the principal specimens show (PI. II, 

 figs. 16-20). 



Billings 5 referred to this genus two species which made confusion for a time, as they 

 possess scarcely any of its characters, but belong to the Taxocrinidae. 



Although Lecanocrinus is thus very satisfactorily defined generically, the discrimination 

 of its species is often very difficult and unsatisfactory. It is a simple form, with not many 

 points of variation to furnish diagnostic characters, and many of the specimens are small. 

 No less than 14 species have been described under this genus or are referable to it, and as to 

 over half of them no assistance whatever can be had from the author's descriptions to show 

 wherein they differ from others. Hence criteria for separation must be independently sought. 

 In general form we have the difference between a concave and convex base ; nearly all the 

 species fall under the latter category, and under it there seems to be every gradation in form 

 of calyx from elongate to depressed, and from conical to globose. Surface characters count 

 for something, and beyond this we must rely on the form and relative dimensions of the anal 

 plate, size of basals, radials and primibrachs, the protuberance of the base, and the character 

 of the column facet. 



The geological range of Lecanocrinus is considerable, beginning with the type species 

 in the Rochester shale, and extending through the Laurel, Waldron, Brownsport, Racine, and 

 Louisville of the Silurian to the Middle Devonian. It is represented in America by seven 



1 Nat. Hist. New York, Paleontology, vol. 2, p. 199. 

 '* Monograph Echinodermen des Eiflerkalkes, 1867, p. 40. 

 1 Lankester's Treatise on Zoology, pt. 3, p. 188. 



4 Iconog. Crin. Suec, 1878, p. 20. 



5 Canadian Organic Remains, Decade 4, 1859, p. 47. 



