THE FOSSIL CRINOID GENUS DOLATOCRINUS AND ITS ALLIES. 43 



Out of 45 specimens in my collection, all of which in other respects 

 are strictly conformable to the type, a single one sporadically has an 

 extra arm in one ray, giving the 11 arms on which Miller and Gurlcy's 

 synonym aspratilis was formed; along with the types in the Gurley 

 collection are about 20 normal specimens of hulhaceus; and these two 

 exceptional specimens are in every other character perfect examples 

 of the species thus so numerously found. Two other of my speci- 

 mens have an extra plate in the second interbrachial range in one 

 area, a variation on which mainly D. argutus was described. The 

 figured type of D. hulhaceus is incorrectly drawn; it is an abnormal 

 specimen, having the posterior interradius irregular, with two plates 

 in the second range like the two specimens in my collection above 

 mentioned; it is of maximum size among specimens of this type, 

 but with it in the Gurley collection as cotypes not figured are two 

 smaller specimens of about average size — namely, 12 mm. high by 

 15 mm. wide. D. aspratilis is almost a counterpart of these two 

 specimens; and I have figured a normal specimen from my collection. 



This was a wide-ranging form, and occurs in the Hamilton of Thed- 

 ford, Ontario, as D. suhaculeatus of Whiteaves, which can not be dis- 

 tinguished from an average specimen of hulhaceus. 



The authors say that D. hulhaceus has no "ovarian pores," and 

 on their supposed absence chiefly proposed their second species, D. 

 pulchellus; but the pinnule openings are present in the three types 

 and in all well-preserved specimens; they are always close under the 

 arm base, not in the open space between, one to each arm on the 

 outside of the dichotom and rarely visible on the inside, as the arm 

 usually becomes free after the first secondibrach. They also note 

 for pulchellus a "difference in general form and surface ornament." 

 The type of D. pulcJiellus is a relatively lower and wider form than 

 that of hulhaceus, the ratio of height to width in the types of the 

 several species being: hulhaceus, 1:1.25; aspratilis, 1:1.2; pulchellus, 

 1:1.5. A few specimens like the latter may be selected out of the 

 general lot, but there would be every gradation between them and 

 the others, all conforming strictly to the type in other respects. R^el- 

 ative sharpness or obscurity of the ornament proves nothing, all 

 being of the same characteristic type, and the difference in promi- 

 nence of sculpturing not being correlated with other characters. 

 Professor Rowley, when figuring a specimen under the name pulchel- 

 lus, says he has little doubt "that D. hulhaceus, D. pulchellus, D. 

 argutus, and D. aspratilis are one and the same species." 



Horizon and locality. — Hamilton limestone: Louisville, Kentucky 

 and vicinity; Thedford, Ontario. 

 183081—21 4 



