1879.] NATURAL SCIENCES OF PHILADELPHIA. 257 



mentions a single anal plate, -which is not to be found in his 

 figure. The presence of anal, interradial, and even axillary plates 

 in I. nobilis which, as far as known, is the latest representative of 

 the genus, is very instructive, as it shows the approach to 

 Forbesiocrinus. In young specimens these plates are undeveloped 

 externally, but are plainly visible on the inner surface of the calyx. 



Phillips, in 1836 (Geology of Yorksh., p. 205), described the 

 genus Euryocrinus, which is possibly the same as Ichthyocrinus, 

 and might be entitled to priority, but his description and figures 

 are so unintelligible that this would be injustice to Conrad. 

 Phillips' generic description reads as follows: "Pelvis opening 

 pentagonal, arrangement of plates like Encrinus, internal cavity 

 very large." Not much better are his figures, since they induced 

 Bronn to consider Euryocrinus as a synonym of Actinocrinus. 



Geological and Geographical distribution. Ichthyocrinus is 

 found first in the Upper Silurian, where it is represented in Europe 

 by 3 species, in North America by 5. None have been observed 

 in rocks of Devonian age. In the Subcarboniferous 3 species 

 have been discovered in America, none in Europe (unless we 

 count Euryocrinus concavus Phillips). 



We regard the following species as belonging to this genus: 



1858. Ichthyocrinus Burlingtonensis Hall. Geol. Rep. Iowa, vol. i., pi. ii., p. 557. 



Lower Burling, liuiest. Burlington. 

 1852. Ichthyocrinus Clintonensis Hall. Geol. Rep. N. Y., vol. ii. p. 181, pi. 41, 



figs. 6 a, b, c. Niagara gr. New York State. 

 1865. Ichthyocrinus Corbis Winchell & Marcy. Memoirs Bost. Soc. Nat. Hist., 



vol. i. , No. 1, p. S9. Niagara gr. Chicago, 111. 



Regarded by Hall as syn. of Ichthyocr. subangularis. 



#1879. Ichthyocrinus Gotlandicus Waehs. & Spr. (Ichthyocr. laevis Angl. not 

 Conrad.) Iconogr. Crinoid., p. 13, pi. 9, figs. 87 a-c, and pi. 22, figs. 20, 

 21. Upper Silur. Gotland, Swed. 



The Swedish specimens, which by Angelin were identified as 

 I. laevis, Conr., are very distinct from the New York species 

 which Conrad described. The European form is pear-shaped in- 

 stead of ovoid, the plates ornamented, but without any surface 

 angularity, and with nearl 3' straight sutures; while the New York 

 specimens have plates with smooth but angular surface, and very 

 distinct waving sutures. We therefore suggest their separation, 

 and propose to call the Swedish form 2". Gotlandicus. 



1878. Ichthyocrinus intermedius Angelin. Iconogr. Crin., p. 13, pi. 17, fig. 7. 

 Upper Silur. Gotland, Swed. 



