152 SMITHSONIAN INSTITUTION 



We have a fragmentary specimen from Gotland, labeled in the Riks Museum C. 

 {heterodactylus ? or ovatus), with only part of the calyx preserved but showing both interior 

 and exterior surfaces free from the matrix ; views of both are given, Plate VII, figures 3a, b. 

 The exterior view, 30, shows small points of three basals, the largest presumably the pos- 

 terior ; but this presents the very unusual peculiarity of not connecting with the anal x, the 

 radials closing in above it instead. The interior view, 3&, confirms this interpretation, all the 

 basals being angular above ; and it shows the further important fact that in this form there is 

 no radianal. It will also be noted that in this specimen the large first interbrachials are not 

 elongate and truncate above, as in many of the others, but are rather broad, and angular 

 above, as if followed by two series of plates. Turning now to figures la-c and 2 on the same 

 plate, representing two perfect specimens from Dudley, it will be observed that they both 

 have the same peculiar base, viz., the posterior basal angular above and not connecting with 

 the anal x; which is a very unusual thing in this group where generally the posterior basal is 

 greatly enlarged and often rises to the full height of the radials. These two specimens have 

 also the same broad, angular interbrachial, followed by two plates — differing in this respect 

 from the other Calpiocrini. The correlation of these two characters gives reasonable ground 

 for assuming the specific identity of the Dudley and Gotland specimens. 



Passing now to the arm structure, we see that the two complete specimens are in about 

 the same stage of development as C. ovatus and C. heterodactylus — the inner branches of the 

 ray being reduced to the size of a greatly enlarged ramule. Having in these specimens — ■ 

 which must necessarily be placed in a distinct species — this condition of arm structure asso- 

 ciated with absence of the radianal, it seems reasonable to suppose a like association to exist in 

 the case of C. ovatus and C. heterodactylus, and that they may therefore upon fairly tenable 

 ground be retained under Calpiocrinus. H. liljevalli, on the other hand, in which the inner 

 arm is somewhat less like an arm and more like a ramule, is placed under Homalocrinus be- 

 cause we find a radianal in one specimen. It is a close question, and if we had a large number 

 of specimens we should probably find a variety of intermediate stages in which these charac- 

 ters would be combined in many distracting ways for our perplexity. The same may be said, 

 however, of all closely related genera, and it is simply a question of expediency — to be de- 

 cided, I think, for each case according to its own circumstances — whether to retain such 

 genera upon their typical forms or to throw them together on account of their close transi- 

 tions. If anyone has devised any exact rule which will regulate all such cases, I have yet to 

 see it. 



As an original proposition, my inclination would be to range all these species under one 

 genus in which, under the influence of high specialization, characters elsewhere important have 

 lost their value. But as the two genera, long ago proposed by Angelin, have been recognized 

 in the literature ever since, it will create less confusion to retain them. 



With this understanding of the real character of the type represented by these two 

 genera, there is little need for comparing them with others to which they have been supposed 

 by various authors to be related. The interbrachials are not so prominent as in Anisocrinus, 

 and there is consequently not that ventricose swelling of the calyx below the arms ; they are 

 large enough, however, to give a marked ovoid rotundity to the lower part of the crown, and 

 the rays therefore do not widen upward from the base as in Ichthyocrinus. There are 

 usually two or more plates in vertical series, but sometimes the first interbrachial in Homalo- 

 crinus is followed by two small plates, or series of plates, abreast ; either form is quite in con- 

 trast to the one huge interbrachial of Anisocrinus. The manner of infolding of the arms also 

 differs ; instead of bending squarely to a broad, truncate summit so noticeable in that genus, 

 they curve more gradually to a rounded and often' narrow apex at a higher point in the arms. 



Homalocrinus is one of two genera of the Lecanocrinidae in which the tegmen has been 

 observed. It is very well shown in a specimen of H. liljevalli found by Mr. Liljevall among 



