154 SMITHSONIAN INSTITUTION 



Homalocrinus parabasalis Angelin 

 Plate VI, figs. 1-12 



Homalocrinus parabasalis Angelin, Icon. Crin. Sueciae, 1878, p. II, pi. 16, figs. 29, 30. — Wachsmuth and 

 Springer, Revision Palaeocrinoidea, pt. I, 1879, p. 35. — Springer, Jour. Geology, XIV, 1906, 

 p. 482, pi. 7, fig. 9. 



Taxocrinus nanus Salter, Cat. Cambrian and Silurian Fossils, 1873, p. 126. 



Homalocrinus dudlcycnsis Springer, Jour. Geology, XIV, 1906, p. 482, pi. 7, figs. 12, 13. 



Type of the genus. 



A small species. Crown ellipsoid, rounding to an obtuse apex above ; gradu- 

 ally expanding from base to about upper IIBr, where height to width is about 

 1 to 1.5 ; at IAx, i to 2.5 ; base broad, truncate, with spread of calyx to IAx about 

 1 to 3. Surface smooth. Maximum crown, 17 mm. high by 12 mm. wide; base, 

 5 mm. ; minimum, 9 by 5 mm. ; average height to width about 1.5 to 1. 



IBB much enlarged, more or less enveloping basals. BB usually visible as 



small triangles, posterior one highest. RR wider than IBr, touching iBr by 



short, sloping shoulders. IIBr 2 or 3; IIIBr 4 or 5; average height to width of 



brachials about 1 to 2.5. Arms above IIBr rounded, generally abutting- but not 



closely packed; ramules on every fourth or fifth brachial, gradually diminishing 



upward. Anal x not larger than other iBr, usually followed by one or more 



smaller plates in vertical series, filling the interradius; interbrachial sutures 



somewhat depressed and brachial plates convex, giving more or less unevenness 



to the general surface. Column short, large, tapering slightly; composed near 



the calyx of prominent short, rounded columnals, with one or sometimes more, 



shorter and narrower ones interposed; all become short and about uniform in 



lower part. 



. Besides the type, only a single specimen has been found in Gotland referable to this 

 species, and in that the growth of infrabasals has entirely covered the basals and lower half 

 of the radials (PI. VI, figs. 2a-c). The posterior basal is not well developed, as the posterior 

 radials meet below the anal plate. This specimen has only two secundibrachs, which is un- 

 usual but occurs exceptionally in specimens from Dudley and also in another species. 

 Angelin's figure of the type specimen (Icon. Crin. Suec, pi. 16, fig. 29) is incorrect as to the 

 arm branching, which is represented as partly equal and partly unequal. 



A careful study of the excellent material at my command has convinced me that there is 

 no constant diagnostic character by which most of the specimens found at Dudley can be 

 distinguished from this species, and that the specific name H. dudleyensis, which I applied to 

 them in 1906, must be dropped. 



The specimens to which Salter gave the manuscript name Taxocrinus nanus belong to 

 this species, as has been clearly shown by examination of two specimens bearing his label as 



types, , in the Sedgwick Museum at Cambridge, England. 



5 2 7 

 As compared with most other species of this and related genera, this may be considered 



fairly abundant, yet it must be remembered that the 17 specimens used in the present investi- 

 gation comprise about all that have been found in nearly a hundred years' collecting at Dudley. 



Type. Angelin's original, and the other specimen from Gotland now figured, are in the 

 Riks Museum, Stockholm. Of those on Plate VI, figures 5, 6, 7 and 8 are in the British 

 Museum, and figures 3, 4, 9, 10 and 11 are in the author's collection. 



Horizon and locality. Silurian, Wenlock Group, horizon d; Wisby, Island of Gotland, 

 and Dudley, England. 



