LECANOCR-INIDAE IQ9 



The weight of evidence in this species is in my opinion rather in favor of a plated 

 integument in the upper part of the anal interradius ; but what makes me hesitate to affirm 

 it as to the other areas is the fact that they are so narrow and the shoulders of the radial for 

 their support so short. In Pycnosaccus, after seeing the first specimen in the British Museum, 

 I never had any doubt that it had this structure, because the spaces for lodging the inter- 

 brachial perisome were so wide and prominent, and I had in mind the unpublished case of 

 Nipterocrinus so closely analogous to it. But in this case I do not feel warranted in proposing 

 a new genus where the basic fact is unproved, and I therefore prefeir to treat this and the 

 next species as variant forms of the genus. The dextrorse twist of the arms and somewhat 

 irregular contour of plates, so characteristic of some species, are wanting in this ; the apparent 

 bending to the right of the middle ray in figure 20a, Plate V, is accidental, not structural. 

 Although the stem is not preserved far enough to show it positively, I suspect that it had 

 merely elongate, cylindrical columnals, like that of M. chapmani. 



Dedicated to the memory of Dr. Otto Thieme, who was among the first to appreciate the 

 wealth of the crinoidal fauna of the Burlington rocks. 



Type. Author's collection. 



Horizon and locality. Lower Carboniferous, Lower Burlington limestone. The speci- 

 men came from a locality famous among the early Burlington collectors, known as " Patter- 

 son Hollow," which produced many of the finest crinoids from the lower bed. They occurred 

 in a layer of rather soft, very even-grained buff limestone, and were of a light, creamy color, 

 easily cleaned from the matrix; and many of them being of delicately ornamented species, 

 they were justly esteemed the most beautiful fossil crinoids ever found. The Barris collec- 

 tion, and the original collection of Wachsmuth, both now in the Museum of Comparative 

 Zoology at Harvard, contain some of the finest of that material. Like nearly all the other 

 choice localities at Burlington, it has by the growth of the city become covered by buildings, 

 and thus lost to the fossil hunter. 



Mespilocrinus chapmani n. sp. 



Plate V, figs. 24a, b 



A large species. Crown subglobose, narrowest below; subpentagonal ; ly 

 mm. high by 17 mm. wide, widest at IIBr; spread of calyx from base to RR, 

 1 to 2.5 ; height to width at RR, 1 to 1.6. 



IBB small. Post. B rising about to height of RR. Height of B to R to 

 IBr, 4.5:4:2.5. RR convex, facets strongly curved. IBr and higher brachials 

 rounded and not in close contact laterally. IIBr mostly 2. Anal x large, filling 

 the interradius. Column large ; proximal columnals short, increasing gradually 

 to fairly long, barrel-shaped columnals, not doubly conical, measuring 4 mm. 

 long by 3 mm. wide. 



This species, like its predecessor, is founded upon a solitary specimen discovered in the 

 City of Burlington in 1906; it is the only one belonging to the genus ever found in the Upper 

 Burlington limestone, with the possible exception of a small specimen M. konincki — thought 

 to be from that horizon. It is of a similar aberrant form to M. thiemei, but the anal side has 

 strictly the structure of the genus. The specimen is flattened, and the interbrachial spaces 

 cannot be seen to their full extent ; but from what is visible, and the strong rounding of the 

 rays, it is evident that the lateral contact prevailing in the genus generally is lacking here. 

 Enough of the column is preserved to show that it does not pass into the extremely long, 

 doubly conical columnals of M. konincki; they are elongate, but simply barrel-shaped, with 



