NO. 2225. NUCULITE8 FROM THE AFAINE SILURIAN— WILLIAMS. 33 



clavicle is distinct, dips forward and reaches half way across the shell. 

 The hinge is crenulate. The posterior end is depressed without dis- 

 tinct unbonal ridge but with obscure traces of corrugations. 



Dimensions, 14 by 6^ mm. = 46%. 



Formation and locality. — Pembroke formation. Thin gray shales 

 at the head of Leighton Cove Goc. 5.3.8. F). 



Remarks. — The type-specimen of this species comes from the same 

 faunule with typical Nuculites corrugatus (loc. No. 5.3.8 F). 



The same species has been recognized in the faunulcs of other 

 locahties of the Pembroke, namely. Oak Hill (loc. No, 1.43.9 A) 

 species No. 2087 A and C and 2089; a mile or so southeast of Oak 

 Hill (loc. No. 1.55.1 A) species No. 1849; northeast of Leighton 

 Point, in the shales continuing Kelley Point outcrops to the southeast 

 (loc. No. 5.4.7 A) species No. 2124, 2125, and 2126. 



Type-specimen.— Cat. No. 62870, U.S.N.M. 



The following three species come from the same shales in which 

 typical Nuculites corrugatus is found Qoc. No. 5.3.8 F). Morpho- 

 logically, they are specifically distinct from that species. Their 

 present form is evidently secondary, not original. They have been 

 figured and given separate names in order to discuss the problems 

 they offer the paleontologist for solution. 



NUCULITES LADON, new species. 



Plate 11, fig. 15. 



Nuculites ladon resembles in its present outline N. hattus, repre- 

 sented in the figure immediately above it on plate 11. It differs in the 

 narrowing of both front and back ends, associated with an arching 

 of the center of the shell, which removes it from a subquadrate to an 

 oval shape. 



It is so near to N. hattus, however, that taken alone one would 

 naturally consider it a variety of that species. It is probable that 

 it is a distorted specimen of N. corrugatus. There are no traces on 

 the umbonal slopes of the corrugations characteristic of the latter 

 species. 



Formation and locality. — Pembroke formation, gray shale at head 

 of Leighton Cove, Goc. No. 5.3.8 F), Leighton Neck, Pembroke. 



Remarks. — The same form has been found in the Pembroke shales 

 outside Leighton Point Goc. No. 5.4.7 B). 



Type-specimen.— Cat. No. 62871 U.S.N.M. 



NUCULITES NESSUS, new species. 



Plate 11, fig. 21. 



The second species, Nuculites nessus, is more like N. corrugatus in 

 its general surface characters, but is a short, high form, with broadly 

 rounded ends, a beak nearly central, high, overarching the hinge, and 

 3343— 19— Proc.N.M. Vol.54 4 



