86 SYNOPSIS OF THE CHARACTERS OF THE 



Pinna in^quicostata. Portk. 



Pinna inasquicostata. Portk. Geol. Eep. 



A few fracrments, probably referrible to this species, Have occurred. It is described as having the radiating 

 ribs broader on one side than on the other, and the sides smooth. 



Pinna MUTiCA. M'Coy. (PL XIX. fig. 11 ). 



Sp.Ch. Cuneifoi-in, four-sided; valves gibbous, obscurely keeled in the middle; surface smooth, with 



obscure, irregular, oblique indentations near the margin of the valves. 



This species has the ordinary wedge-shaped, four-sided figure of most of the genus, the two dorsal planes 

 are the narrowest, the mesial ridge of the valves is very obtuse ; this scarce species is easily known from the 

 other PinncB of the Palaeozoic rocks, by the plainness of its surface. Length, when perfect, probably about 

 three inches. 



LiNGULA. 



Qeyi. Ch. Longitudinally oblong, equivalve, equilateral; beaks terminal, pointed, gaping; front margin 



subtruncate, gaping; attached by a fleshy pedicle, passing out between the beaks. 



LlNGULA MARGINATA. Phil. 

 Lingula marginata. Phil. Geol. York. 

 Sp. C/(.— Oblong, twice as wide as long, sides straight, parallel, convex; front margin subtruncate; pos- 

 terior end obtusely rounded; slightly mucronate in the centre; surface marked with lines of growth parallel 

 with the margin. 



Distinguished from the L. parallela, Phil., by its truncated front, and straight sides. Length half an inch. 

 Some of the specimens shew traces of the pedicle of attachment. 



LlNGtJXA PARALLELA. Phil. 



Lingula parallela. Phil. Geol. York.— Lingula parallela. Portk. Geol. Eep. 



Sp. CVi.— Oblong, convex, twice as long as wide; sides nearly parallel, slightly convex ; front convex; 

 posterior end elliptical, pointed. 



Several specimens have occurred, apparently referrible to this species, but the various fossil species o£ Lin- 

 gula are so ill defined, and resemble each other so closely, that without very perfect specimens it is difficult to 

 identify them. 



Lingula squamifoemis. Phil. ? 



Lingula squamiformis. Phil. Geol. York. (?) — Lingula squamiformis. Portk. Geol. Rep. 



Sp. C/(.— Oblong, width rather more than half the length; sides straight, parallel; front subtruncate; pos- 

 terior end obtusely rounded ; slightly acuminate in the middle ; convex ; depressed towards the front margin ; 

 surface with irregular, concentric lines of growth. 



The specimens corresponding to these described by Captain Portlock are exceedingly abundant in cer- 

 tain localities. I have never seen a specimen so wide in proportion to the length as that figured by Professor 

 Phillips ; there may, however, be varieties. Length, ten lines, width six lines. 



Anomia. Linn. 

 Gen. CA.— Shell very thin, irregular, inequivalve, perlaceous, attached by a calcareous mass passmg 

 through a foramen near the beak of the lower valve, which is fiat or concave, the other convex. 



