LECANOCRINIDAE 147 



actual relation of the two sets of plates is shown in specimens like Plate VIII, figure "jc, 

 where the infrabasals have been partly removed, and the basals, three out of the five, are 

 plainly visible beneath them. In this specimen the infrabasal development went to the ex- 

 treme, covering the radials, the larger part of the first primibrachs, and part of the first inter- 

 brachials. The structure is also well shown in figure lb, on the same plate, where the 

 overgrowth is less extensive; here the radials are not covered, and the posterior basal is 

 slightly visible, while the other basals are concealed except at two places where the edge of 

 the infrabasals has been broken away leaving the points of two basals just peeping out. 

 Another very instructive specimen is that figured on Plate VII, figures 3a, b, which are ex- 

 terior and interior views of the base; it shows that the infrabasals, while developed in this 

 extraordinary way on the exterior, retain internally their relative position in the calyx wall, 

 and still lodge the axial canal. It is possible that the relative size of the plates is not quite 

 correctly shown by this specimen, and that the thin edges of the basals, meeting one another 

 laterally, have been somewhat cut away in cleaning the internal surface ; the chief surface of 

 apposition of these plates is the outer, or dorsal, surface of the basals, and not their inner 

 face which became quite thin. A vertical section corresponding to figure 3b shows how this 

 is ; Plate VIII, figure 8. The same structure is further shown by figure 4b on Plate VIII, 

 where the infrabasals are gone, leaving the large pentagonal open space within the ring of 

 basals which they filled, and also the imprint of their outward extension which covered the 

 basals except at small points ; this must be considered in connection with figure 4a, a lateral 

 view of the same specimen, which shows how the basal plates slope inward toward a rather 

 thin edge. These three specimens are also valuable because they show positively the absence 

 of any radianal, the importance of which will be seen when we come to the case of 

 Homalocrinus. 



Now this peculiar basal structure is exhibited in various degrees of development in the 

 excellent material at our command. In some cases two or more of the basals are visible as 

 mere points (Pis. VII, fig. 3a; VIII, figs. 2c, 3). In others, and more frequently, the posterior 

 basal which is higher than the others, rising almost to the level of the radials, is alone visible 

 beyond the infrabasals (PI. VII, figs. 4c, 5<i). In still others no basal at all is to be seen, and 

 the large infrabasals appear to be directly surmounted by the radials (PL VIII, fig.- 5a) ; 

 then the radials almost disappear, and the interbrachials touch the infrabasals by their points 

 (fig. 6a) ; and finally the entire radial, with part of the next plate and the lower angle of the 

 interbrachial, are covered over by the upward growth of the infrabasals which form a convex 

 ring like a high, rounded columnal (PL VIII, figs, jb, c). Nevertheless, the basal elements 

 of the calyx are seen to be the same as those of the group generally. There thus remains no 

 longer any doubt of the real structure of the genus, and it must be considered as representing 

 a definite, though extravagant and therefore short-lived, modification of the crinoid plan in a 

 direction not heretofore observed. 



This specialization is shared, however, by the allied genus Homalocrinus, in which are 

 exhibited certain transitional features leading up to the fully developed Calpiocrinus which 

 are of considerable interest. Angelin's diagnosis of Homalocrinus represented a dicyclic 

 crinoid with ovoid body, abutting arms, and " interradial " plates, which was not enough to 

 establish a genus when compared with Ichthyocrimis as at that time understood. He did not 

 mention any odd plate such as might constitute a radianal, as he did in his diagnosis of 

 Lecanocrinus immediately following, where he said " parabasalia sex " ; but he put the two 

 genera into one family called the Homalocrinidae, including also Clidockirus, Calpiocrinus 

 and Anisocrinus. Pie also mentioned under Homalocrinus that the arms were " dichoto- 

 mous," being thus different from those of Calpiocrinus which he described as being " un- 

 equally dichotomous." His description of the only species added nothing to the generic 

 definition. His figure of H. parabasals (Icon. Crin. Suec, p. n, pi. 16, fig. 29) showed the 



