LECANOCRINIDAE 1 51 



genus. There remain C. heterodactylus, C. ovatus, and C. Umbriatus, which appear in this 

 order in the Iconographia. Angelin did not designate any type species, and it seems prob- 

 able from the statement of Lindstrom and Loven in the introduction to that work that the 

 order of arrangement of the species was theirs, and not Angelin's. In these circumstances, if 

 a generic definition can be made out for Homalocrinus from the characters disclosed by its 

 known species, and if it be further found that the species referred by Angelin to Calpiocrinus 

 do not agree with each other as to the corresponding character, but that some of them in this 

 respect approach Homalocrinus as now denned, — then it seems to me that any species remain- 

 ing which clearly differs from the latter in the character in question will be the true Calpio- 

 crinus; otherwise Calpiocrinus, being the second of the genera in order of publication, would 

 have to be dropped altogether. 



Now it so happens that one of these species, C. Umbriatus, meets the last condition, and 

 also contains within itself the most complete development of the one character mentioned by 

 Angelin which is left for the genus, viz., the unequally dichotomous arms. And when in addi- 

 tion to this it is remembered that this particular form of heterotomous arm is associated with 

 the lack of a radianal, while its presence is correlated with the other form of heterotomy in 

 the typical species of Homalocrinus, it would seem that upon these facts the genus may be 

 logically maintained, with C. Umbriatus as its type species. 



The position of C. ovatus and C. heterodactylus remains to be settled. There is but a 

 single specimen of each that is certainly known to belong to them, viz., the respective types, 

 which I have carefully refigured on Plate VII giving four principal figures of each besides 

 some details. The two specimens are of similar type, except that in general form one is more 

 ovoid than the other. In each the basals are completely covered by the infrabasals, except 

 the truncate apex of the posterior basal which connects with the anal plate ; no radianal is 

 visible, but this does not prove that it is wanting, because the development is such as to con- 

 ceal it even if present in the same form and size as in Plate VII, figure 3. In both, the rays 

 divide a second time on secundibrachs 3 or 4 into two nearly equal divisions, the outer one of 

 which bears conspicuous ramules, with bifurcations plainly visible from the dorsal side ; while 

 the inner, although large and rising to the full height of the outer one, shows little evidence 

 of lateral ramules from the dorsal side. They are present, however, though much smaller, 

 and are given off from small shoulders of the axillary tertibrach toward the ventral side. 

 This is well explained in C. ovatus by figure 4/, Plate VII, an enlarged side view of the axil 

 on the exposed inner arm of figure 4a, and by figures i\d, e showing the axil seen from above 

 and from the side at b on another inner arm. The same structure for C. heterodactylus is 

 shown in figure 50, where b and c are axils on the inner arm seen partly in a side view, and a 

 a much larger ramule on the outer arm on which also the bases of ramules are plain enough 

 from the dorsal side. The difference between the inner and outer branches is somewhat less 

 in figures 50, b than in 4 a, b. 



Hence there is in these specimens an arm structure which is of a character similar to that 

 of Calpiocrinus as typified by C. Umbriatus, but not quite the same. It is a departure iri a 

 direction which if continued far enough would result in the disappearance of the inner arm 

 by reduction to the grade of a simple, unbranched ramule of size proportionate to the others 

 following it. This would leave the ray composed of only two ramuliferous trunks, as in 

 Homalocrinus parabasalis. Conversely, as already stated, the change might result from the 

 progressive enlargement of the lower ramule of Homalocrinus. These specimens, therefore, 

 may represent morphologically degraded Calpiocrinus, or advanced Homalocrinus. If we 

 knew positively the fact about the radianal in them the line might be more satisfactorily 

 drawn. While we cannot, as already explained, say whether it is or is not present in speci- 

 mens like these, we must do the best we can with indirect evidence. 



