LECANOCRINIDAE 187 



Pycnosaccus bucephalus (Bather) 

 Plate XII, figs, io-ii 



Oncocrinus bucephalus Bather, Ann. and Mag. Nat. Hist., (6)V, April, 1890, p. 334, pi. 14, fig. 31; 

 ibid., May, p. 387. 



A large and robust species. Similar to P. scrobiculatiis, but with more 

 massive crown and heavier arms. Calyx more rotund, without sharp angles, 

 with costae much broader and rounder, and no ridge connecting RR ; it is some- 

 what lower proportionally — height to width in two specimens being about 1 to 

 1.8; spread of calyx from base to top of RR, I to 3. Maximum crown, 40 mm. 

 high by 30 mm. wide; base, 10 mm. 



IBB low, nearly flat, not contracting above column facet. R facets wide, 

 their width to that of R as 1 to 1.55; but little elevated and without projecting 

 rim. IBr 1 ; IIBr 2 or 3, and sometimes one. Arms heavy, rounded. Column 

 very large, almost as wide as the infrabasal ring; composed of strong, rounded 

 columnals, with shorter and narrower ones irregularly interposed. 



This species was named by Dr. Bather without description as the type of his proposed 

 genus Oncocrinus, which he afterward placed as a synonym under Pycnosaccus (Lankester's 

 Zoology, pt. 3, p. 187), and the specimens upon which it was founded have been courteously 

 placed by him at my disposal. These consist of two fine individuals from Dudley, originally 

 in the collection of John Gray and now in the British Museum, which are to my knowledge the 

 only ones found. The species agrees with P. patei in having uniformly one primibrach, but 

 has a much broader base and larger column, entirely lacking the contraction of the infra- 

 basals so characteristic of that species. It is in every way more robust, the calyx ridges 

 stronger, and the arms heavier and rounder. It is, of course, closely related to that as well as 

 to the Swedish species — the three being from closely correlated horizons, and doubtless 

 representing merely changes due to migration. One of the specimens has an asymmetry of 

 the calyx similar to that mentioned under P. patei. 



Types. In the British Museum. 



Horizon and locality. Silurian, Wenlock Group ; Dudley, England. 



Pycnosaccus tenuibrachiatus n. sp. 



Plate XIII, figs. 1-2 



A medium-sized species, resembling P. patei, but with more delicate and 

 slender arms. Calyx of about the same proportions, but appearing higher 

 because the arms do not extend quite so high up; base broader, spread of calyx 

 from base to top of RR, 1 to 3. Side outline curved ; ridges obscure. Maximum 

 crown 26 mm. high by 20 mm. wide; base, 7 mm. 



IBB low, not contracting above column facet. R facets very narrow, their 

 width to that of R as 1 to 2.5 ; not elevated, shallow and but little indented ; distal 

 margins of RR almost perfectly straight. IBr 1 ; IIBr 2 and 3. Arms round, 

 very short and slender. Column unknown. 



This species, from a higher horizon than any of the preceding, is one of the two latest 

 representatives of the genus, bringing its range into the Devonian. It is well distinguished 

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