NO. 2225. NUCULITES FROM THE MAINE SILURIAN— WILLIAMS. 43 



In the second figure {N. atreus) the squeezing has not greatly 

 affected the angular position of the parts, as shown by the nearly 

 normal relation of the axes A-B to C-D (90°); but has apparently 

 thrust the front half of the shell upward and forward, elongating the 

 part in front of the beak, while the posterior basal part has been forced 

 upward toward the beak, thus shortening the posterior end- 

 In the third figure (N. thijestes) the arcs A-C and D-B have been 

 reduced about 20°, with corresponding increase of the arcs A-D and 

 C-B. But the effect of this squeezing has been very different from 

 the first case, because of the different position of the beak, which was 

 evidently more stable, the other parts of the shell moving about it. 

 The result has been a great flattening out of the front half of the shell, 

 a shortening and pushing forward of the posterior part, arching of 

 the hinge margin, and thrusting of the beak into a nearly central 

 position, leaving the clavicle in a normal relation to the beak. 



NUCULITES AMYOUS, new species. 



Plate 11, fig. 5. 



Shell narrow, elongate, with a high, angular umbonal ridge. The 

 beak low, terminating at about one-quarter distance back from front 

 to posterior extremity. The umbonal ridge forms the most elevated 

 part of the surface in the middle where it is sharply angular and flat- 

 tens out both toward the beak and toward the postero-basal angle. 

 On the posterior slope there is a shghtly raised secondary parallel 

 ridge. Anterior to the umbonal ridge, the surface slopes off grad- 

 ually toward the front. The clavicle, inclines shghtly backward, 

 and extends scarcely halfway to the base. 



Dimensions. — Antero-posterior diameter 13^ mm.; height, 7 mm. 

 (52 per cent). There is a faint Unear depression in the specimen 

 (which is a mold of the interior) proceeding from behind the tip of 

 the beak, crowning the umbonal ridge near its cardinal end, and 

 terminating on the basal margin at a point about 3 mm. in front of 

 the posterior extremity. This depression appears to have been a 

 raised line on the interior of the shell about one-half the strength of 

 the clavicle. It is possible that it is the expression of a crack of the 

 shell, as its direction is parallel to the axis of elongation of the rock 

 in which it lies. 



Formation and locality. — Pembroke formation, gray splintery shales 

 in the vicinity of Oak HiU, northwestern Pembroke (loc. No. 1.43.9 

 A). 



Type-specimen.— C&t. No. 62885, U.S.N.M. 



NUCULITES BATTUS, new species. 



Plate 11, figs. 11 and 13. 



Shell thin, subquadrate, flattened, height more than half the 

 antero-posterior diameter. Both anterior and posterior ends broadly 



