I48 SMITHSONIAN INSTITUTION 



arms both equally and unequally dichotomizing ; and as there was nothing decisive in either 

 generic or specific diagnosis or figures to distinguish it, Wachsmuth and Springer placed it as 

 a subgenus under Ichthyocrinus (Rev. Pal., pt. 1, p. 35). Bather in 1900 (Lankester's 

 Treatise on Zoology, pt. 3, p. 189) separated Homalocrinus from the Ichthyocrinidae because 

 of its infrabasals, and placed it in his family Taxocrinidae on account of what he supposed 

 from Angelin's figure to be isotomous arms. A correct figure of the type specimen of 

 H. parabasalis (PI. VI, figs, la, b) shows that it has heterotomous arms, with ramules borne 

 on ten main ray divisions, or rami, and a small radianal lying under the right posterior ray 

 between the two basals and meeting the infrabasals. These are the characters which estab- 

 lish its position as a valid genus, and by which it must be distinguished from Calpiocrinus, 

 with which it is associated in the remarkable specialization of the basal structures. 



When I proposed my brief preliminary analysis of this group in 1902 (American 

 Geologist, vol. 30, p. 95), I mentioned certain specimens froni Dudley which had been identi- 

 fied as Calpiocrinus, but which on account of the presence of a small radianal observed in 

 them, and of plainly developed basals, I thought might belong to a new genus for which I 

 suggested the name Leiocrinus. Homalocrinus was placed in a group with isotomous .arms, 

 following Angelin's figures, near Clidochirits. The first drawing made for me by 

 Mr. Liljevall from the type specimen of H. parabasalis (PI. VI, fig. la) disclosed a heter- 

 otomy of its arms, which led me then to suppose it must be congeneric with Calpiocrinus. 

 A later more detailed study of the base brought out plainly the presence of a small radianal 

 under the right posterior radial (PL VI, fig. id). In this specimen the basals are plainly 

 visible, and it became at once evident that most of my Dudley specimens would fall readily 

 under Homalocrinus as characterized by its type specimen and not by former erroneous 

 figures or faulty diagnosis. This I pointed out in my " Further Remarks " in 1906 (Jour. 

 Geology, vol. 14, p. 482), with illustrative figures, and proposed for the Dudley specimens the 

 name H. dudleyensis. Since the publication of that paper I have accumulated considerable 

 additional information and material relative to this interesting form, including a new species 

 from Gotland, and am now enabled to make quite plain the generic position of Homalocrinus, 

 which was still not entirely clear when I prepared the above-mentioned account of it. It is 

 from the study of a good series of specimens of the Dudley form that the most important 

 light has been obtained. Of these there are nine in the British Museum — where they are 

 known as Calpiocrinus — which I personally examined; two in the Sedgwick Museum at 

 Cambridge, England, of which I have photographs and sketches of the essential details ; and 

 six of my own; — making seventeen in all from the rocks of the Wenlock age at Dudley. Of 

 these I have figured on Plate VI four from the British Museum and four from my own col- 

 lection, which thoroughly illustrate the puzzling variations of the species ; and there are also 

 shown two other interesting allied Dudley specimens on Plate VII which fall under another 

 species. The study of this series of specimens in connection with the material from Gotland 

 has led to the conclusion that most of the Dudley specimens are only variant forms of 

 Angelin's original species, H. parabasalis, and that no reliable diagnostic characters can be 

 pointed out to warrant the retention of the specific name which I proposed for them. While 

 I regret that this long campaign of education as to this form has encumbered the literature 

 with two useless names, the names are gladly abandoned in view of the more important results 

 obtained. 



The two decisive generic characters of Homalocrinus, as already stated, are the heter- 

 otomy of the rays by subordinate branching from the first main division, and the presence of 

 a radianal within the ring of basals. Looking at the figure of Calpiocrinus Umbriatus 

 (PL VIII, fig. la), it will be seen that the ray bifurcates into two equal divisions, and each 

 of these divides again into two main branches, or rami, of about equal size, from the inner 

 side of each of which are given off three or more lateral ramules. In Homalocrinus para- 



