340 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.45. 



of our specimens shows a very fine sculpturing which is reproduced 

 (magnified about 3 diameters) in our figure 18 on plate 30. The 

 definition of L. lewisii given by Davidson is in part, namely, ''Sub- 

 quadrate, oblong, longer than wide; sides almost parallel; front 

 very shghtly rounded; beaks obtusely angular; valves almost equally 

 deep, the convexity very small." This apphes to our shell. The size, 

 " 14 by 10 b}'' 2^ fines," refers to the larger, not the smaller figures 

 given by Davidson. His figure No. 2 measures 23 by 17 mm. 



Our figured specimen measures 19 by 14, and a larger specimen 

 from same locahty measures 21 by 17 mm. Our shell differs, how- 

 ever, in surface sculpture. The concentric growth-ridges are much 

 as in L. lewisii, but in addition to them our species is marked also by 

 very sharply cut strise crossing the shell, across the middle nearly 

 parallel to the front border, but dropping downward on the sides 

 where they appear as radiating from a point somewhat anterior to 

 the beak. The strias are undulating and on sides appear hke can- 

 cellations from the crossing of the concentric strias which there come 

 close together. There are 24 of them to the centimeter in center of 

 the magnified figure giving about 72 to the centimeter in the natural 

 size shell. An inner layer of shell shows fine elevated radiating 

 lines near the front, but these are not in evidence on the inner surface 

 which appears smooth. 



The surface sculpture is similar to that seen on the New York 

 Devonian species Lingula punctata Hall; and a similar sculpturing 

 is described for L. granulata and L. tenuigranulata of the Ordo- 

 vician.^ The shell is larger, more quadrate, and in form differs 

 from the species L. cornea Sowerby which occurs liigher up both in 

 British rocks and in the formations about Eastport, Maine. It 

 resembles the Clinton form L. ohlata Hall, but is a much larger shell. 



Formation and locality. — Pembroke formation, in the shales out- 

 cropping at head of Leighton (Schooner) Cove on south end of the 

 Pembroke peninsula, Waslfington County, Maine (loc. No. 5.3.8M^). 



Eolotype.—Csit. No. 58967, U.S.N.M. 



LINGULA MINIMA var. AMERICANA, new variety. 



Plate 31, fig. 6. 



Cf. 1839. Lingula minima Sowerby, Sil. Syst., p. 612, pi. 5, p. 23. 

 1866. Lingula minima Sowerby, Davidson, Brit. Sil. Brae, p. 48, pi. 2, figs. 

 36-44. 



Sowerby neither by his definition nor his figures made it clear 

 wherein L. minima differs from L. cornea, and M'Coy regarded them 

 as identical, saying at close of definition of the species L. cornea, "The 

 L. minima does not show the shghtest difference that I can perceive."' 



» Davidson, Brit. Sil. Brach., pp. 36 and 37. « Brit. Pal. Foss., p. 251. 



