NO. 2225. NUCDLITES FROM THE MAINE SILURIAN— WILLIAMS. 37 



The figures of Cucullaea antiqua given by Sowerby are 8h and 14 

 mm. long, with height about 70 per cent and 64 per cent of length. 



McCoy gives the proportion 65/100 for height to length, thus show- 

 ing, mathematically, the more slender form of our species. 



Formation and locality. — Pembroke formation, gray shales on east 

 side of Young's Point, Denbow Neck, Lubec (loe. No. 5.25.4 B). 



Type-specimen.--Cat. No. 62876, U.S.N.M. 



NUCULITES CRASSUS, new species. 



Plate 12, figs. 16 and 17. 



The definition of this species is founded upon two molds of the 

 interior of left valves and a fragment of the exterior. 



Shell large, long, elongate-ovate, anterior and posterior ends about 

 equally narrowly rounded. A deep, bioad posterior furrow on the 

 exterior runs from the hinge to the basal margin separating ofl: the 

 strong umbonal ridge from the body of the shell. In the mold of 

 interior the shell seems to have been thickened for a vridth of several 

 millimeters in front of the posterior adductor, which is deeply im- 

 pressed. The clavicle is strong and expanding at the inner surface 

 of the shell; and extends more than halfway across the shell. The 

 basal margin is broadly, evenly rounded up to the edge of the pos- 

 terior furrow, which ends in a sinus. The surface curves down 

 abruptly at both the anterior and posterior ends. The crenulations 

 are strong both sides the beak. The beak arches over the hinge. 



The exterior surface is marked by fine concentric lines. 



Dimensions, 37 by 15^ mm. (41i per cent); 30 by 13 (43 per cent). 



The teeth behind the beak distinctly express the "V-shaped form" 

 which Verrill and Bush considered to be a characteristic of modem 

 genera ot this group of shells.* 



Formation and locality. — Pembroke formation, gray splintery 

 shales on east side of Denbow Point, north side of a httle cove on north 

 side of Young's Point. Lubec (loc. No. 5.24.6. B). 



Remarks. — This is a large, thick shell, having about the propor- 

 tions of A"^. rohustus but twice as large. Our specimens are larger 

 than the largest reported specimen of Nuculites ohlongatus Conrad, 

 and proportionally the shell is longer and narrower. The height of 

 two specimens of N. crassus is 41 per cent and 43 per cent of the length. 

 The corresponding proportion of N. ohlongatus is 57 per cent. 



It agrees with N. rohustus in the strong reinforcement of the inner 

 surface of the sheU between the umbonal cavity and the posterior 

 muscular scar, the narrowing of the posterior end, and the flattening 

 of the umbonal and central cavity of the shell shown in the interior 

 molds. In these features, the resemblance to Cucullaea antiqua Sow- 

 erby is closer than to the Devonian iV. ohlongatus Conrad. 



Type-specimen.— C&t. No. 62877 U.S.N.M. 



« Amer. Jour. Sci., vol. 3, 1897, p. 5S. 



