WHITEAVE6. J FOSSILS OF HAMILTON FORMATION OF ONTARIO. 371 



(page 311), Messrs. Waohsmuth and Springer say that they have been 

 unable to get authentic specimens of Hall's C'acabocrinus lampJlosus 

 and C Troostii, and that the descriptions of them are too general for 

 specific determination. Moreover, the original types of C. lamellosus are 

 stated by Hall to be from the Upper Helderberg limestone. 



Dr. S. A. Miller, who has examined this specimen also, has convinced the 

 writer that it really has seventeen arms, its arm formula being 

 4 + 3 + 3 + 3 + 4=17, and thinks that it should be regarded as the type of 

 a new species. It is, however, unfortunately too imperfect to admit of a 

 satisfactory description of its characters, although previously but incor- 

 rectly represented as "nearly perfect," when most of its surface was 

 covered by the matrix. 



DoLATOCRiNUS. (Species uncertain.) 



Perhaps a var. of D. tuherculatus, Wachsmuth and Springer. 



Cfr. Dolatocrinus tuherculatus, Wach.smuth and Springer. 1S97. N. Amer. Crinoide.i 

 Camerata, vol. I., p. 324, pi. 25, fig. 3. 



A single specimen of a large Dolatorrinus with a surface ornamentation 

 differing materially from that of the preceding species, but which does 

 not show the arm formula?, was collected at Thedford by Mr. Kearney in 

 1895 and is now in the Museum of the Survey. The dorsal cup of this 

 specimen is apparently similar to that of D. tuherctdatus in size, shape 

 and sculpture, but the prominent circular rim at the base, which encircles 

 the upper part of the column, is proportionately larger and thicker, so that 

 the five large pointed tubercles which surround it, almost touch its outer 

 edge and are not placed at some distance from it. In the type of D. 

 tuherculatus, as figured in the monograph cited, the basal rim is about six 

 millimetres and a half in its maximum diameter and the summits of the 

 five large tubercles nearest to it are about five mm. from its outer margin. 

 The basal rim of the Thedford specimen is fully ten mm. in diameter and 

 the summits of the five large tubercles nearest to it are not more than 

 two mm. from its outer margin. Although the external sculpture of this 

 specimen is well preserved, the sutures between the plates of which the 

 dorsal cup is composed are entirely covered by the matrix, so that it is not 

 yet practicable to compare the number and relative shape of these plates 

 with those of D tuherculatus. 



Nothing is known of the ventral disk or arms of that species, and of 

 the Thedford specimen all that is preserved is a large portion of the dorsal 

 cup, with most of the upper part of one of the rays. On the left side of 

 this ray there was clearly one arm, but on the right side it is scarcely 

 practicable to decide whether there was one arm or whether there were 

 two. 



