ICHTHYOCRINIDAE 289 



The differences of proportion in general contour would be emphasized if we had the 

 external surface instead of merely the internal casts of /. corbis, because the calyx wall is 

 thinnest below the secundibrachs ; but the dimensions above given are sufficient to prove that 

 the two species are about as different in type as we can expect to find in a genus like Ichthyo- 

 crinus. Hall's Bridgeport specimen, as the table shows, falls into line with the Waldron 

 specimens, and not in any respect with those from Chicago. It also exhibits in a marked 

 degree the angularity in the lower part caused by the prominence of the brachial series. This 

 feature is usually absent in the Chicago casts, though some specimens of /. corbis show it 

 to a slight extent. In my specimen (PL XXXVI, figs. 6a,'b) which has the plates in the 

 halves of two contiguous rays preserved from IIBr 2 up, and which is of maximum size, there 

 is only the faintest trace of a median ridge, although the higher ray divisions preserved in 

 other rays are more or less angular on the dorsal side. But in the internal cast of /. sub- 

 angularis from Bridgeport, in addition to the characteristic dimensions given in the fore- 

 going table, the figure (PL XXXIV, fig. 8) shows the radial angularity and peculiar contour 

 of the base, precisely as in the Waldron specimens. This specimen is better than Hall's in 

 that it has the outline of the base perfectly preserved, even to the cast of the axial canal. 



Hall in the discussion with Winchell and Marcy (20th Report, p. 385) mentions one of 

 the casts showing " the obscurely angular form of the lower part of the body." This speci- 

 men, which lies in the same tray with his type from Bridgeport in the Hall collection at the 

 American Museum, undoubtedly shows the angularity mentioned with considerable dis- 

 tinctness. It has but little of the usual distortion of /. corbis, and it is interesting" to find that 

 its proportions are intermediate between those of the two species. It is rather singular that 

 of the only two specimens from the Chicago beds obtained by Hall, one should be a good 

 example of /. subangularis and the second a very evident intermediate type ; neither of them 

 represents the prevalent form, and after seeing them we can readily understand why Hall 

 insisted on the specific identity of the species from the two areas. 



In the List of Types published by the American Museum the locality of Hall's figure 15, 

 plate 1 1 of the 20th Report is given as Racine, Wisconsin, although Hall himself stated it as 

 Bridgeport. This locality is within the present limits of the city of Chicago, at about the 

 intersection of Thirty-fifth street and Archer avenue. I am informed by Mr. E. E. Teller 

 of Milwaukee, President of the Wisconsin Natural History Society, who knows the history 

 of all the collections ever made in the Illinois- Wisconsin Niagaran area, and has himself 

 made extensive collections there, that Ichthyocrinus has never been found at any other local- 

 ity than Bridgeport, where it occurred in the uppermost layers of the quarry. It does not 

 occur at Racine, or other well-known Wisconsin localities, and the enormous excavations 

 made during the construction of the Chicago drainage canal have not to my knowledge pro- 

 duced a single specimen. 



The imbrication of the plates produced by the raised transverse margins of the brachials 

 is present in two of my specimens of /. corbis having part of the plates intact; it is less evi- 

 dent on Hall's Bridgeport specimen, and not at all on those from Waldron. 



I have not been able to find in any specimen of /. corbis the least trace of the inf rabasals, 

 though in several the bounding sutures of the basals are beautifully distinct, and there is seen 

 projecting from them the obtusely angular object which Winchell and Marcy took for the 

 stem (PL XXXVI, figs. 30, b). There is little doubt that the infrabasals in this species were 

 in the same condition as those of /. gotlandicus, very small and largely atrophied, and that 

 this projection is the cast of the enlarged axial opening left after their resorption (compare 

 Pis. XXXV, figs. 4&, 5, and XL, gb). It is perfectly preserved in the specimens above men- 

 tioned, distinctly showing the pentapetalous outline at the lower end ; and it is further inter- 

 esting because the length to which it projects, which is not over a millimeter, no doubt 

 represents the full thickness of the calyx wall at the base. This is but little greater than is 



