240 NEW YORK STATE MUSEUM 



the series or stage of development in which the correspondence therewith is 

 complete. The latter terms of the series represent development beyond 

 that attained by the type, it is metatypical. Hence we may with propriety, 

 in instances of this kind which may arise in the comparison of provincial 

 faunas, employ the term metatype ; thus 



Chonetes hudsonicus metatype gaspensis 



Billings observed the presence of cardinal denticulations in C h. 

 m e 1 o n i c u s and Hall has shown that crenulations exist on the hinge line 

 of C h. arcuatus, Onondaga limestone [see Palaeontology of New York, 

 1867, 4 : 119, pi. 20, fig. 7, e, fj but explained them as due to the projection 

 of the cardinal spine tubes. Whether or not this can be made to account 

 for their existence in that species it would hardly meet the condition in the 

 Gaspe specimens. 



The variation in these expressions of Chonetes within the series above 

 described, may be taken as an indication of the prolixity which would 

 attend development at a center of migration. Chonetes hudsonicus 

 alone, so far as our knowledge goes, expresses that part of this line of 

 development which has wandered far. 



Localities. Portage road, 3 miles west of Gaspe Basin and loose on 

 the east side of the Southwest Arm of Gaspe Bay. 



Chonostrophia dawsoni Billings 



Plate 46, figures 14-24 



Chonetes dawsoni Billings. Palaeozoic Fossils. 1874. v. 2, pt i, p. 18, fig. 8 

 Cf . Chonostrophia c o m p 1 a n a t a Hall. \^See ante p. 210] 

 Billings's description of this species was as follows : 



Shell semielliptical; width about one third or one fourth greater than the length; 

 cardinal angles usually somewhat less than a right angle; sides, for about one third or one 

 half the length below the hinge line, nearly straight, or gently convex; slightly converging 

 towards each other, and then gradually and uniformly curving to the front margin which 

 is broadly rounded. 



Ventral valve gently concave, or nearly flat; the umbo slightly elevated; beak 

 scarcely distinguishable from the cardinal edge. On the latter are from six to ten short 

 spines on each side of the beak, sloping outwards at an angle of from 45° to 60°. The 

 cast of the interior of this valve shows that there is a thin elevated ridge or septum, 

 extending from the beak along the median line, about half the length of the shell. Two 

 other obscure ridges diverge from the beak outwards, forming an angle of between 30° and 

 40° with the hinge line. The area has not been seen, but its impression shows that it is of 

 moderate size, and inclined at an angle of about 45° to the plane of the lateral margin. 

 Foramen triangular, the width apparently a little greater than the hight. 



The dorsal valve has not been seen. 



The surface is covered with fine subangular radiating striae which increase by fission 

 and intercalation. Of these there are from seven to nine in the width of one line. There 



