218 ORGANIC REMAINS. 



specimen, containing- one of the shells with both valves entire, nearly 

 half of another, and portions of two or three more ; together with 

 vestiges of cavities, now empty, worn by shell-fish of the same spe- 

 cies. The shells are in the state of spar, of a yellowish colour, thin 

 and brittle. 



The M. ediilis, or common muscle, occurs in several parts of the 

 strata. No. 3 is a beautiful pyritous specimen, from a nodule in the 

 alum shale. No. 2 is another handsome muscle, from the calcareous 

 sandstone; differing a little from the common muscle, especially at 

 the beaks, where it resembles the M. curtus, or young M. modiolus. 

 The latter occurs in the oolite, in its largest size, and with very thick 

 spathose valves. No. 10, which is also from the oolite, appears to be 

 the 31. ungulatus. No. 4 is the 31. avicula, or a variety of 31. hirun- 

 do, from the Malton oolite. Small shells, resembling the 31. lingua, 

 and others in the form of M. margaritifera, or 31. unguis, are found 

 in the oolite, in the ironstone, and in the aluminous strata. 



Fig 7 represents a curious cast, from the Kettleness or Staiths 

 bands, or the beds most nearly corresponding with them in the front 

 of Cold mo or. Its general shape approaches to that of the M. 

 modiolus ; but, besides the proper beaks, it has on the anterior slope 

 two secondary beaks, or prominent inflections of the umbones, which 

 standing up like ears, give that end of the shell an appearance re- 

 sembling the head of a horse. It seems to be akin to 31. vulgaris, or 

 31. plicatiis. 



Analogous to this shell is No. 9, which is a cast from the oolite. 

 It has on the anterior slope two large folds of the umbones, which 

 diverging from the hinge again converge, so as nearly to meet, 

 inclosing a kind of cylindrical channel. The base of the shell is 

 rather truncated and keeled. The posterior slope is also keeled; 

 and at the beak end are two large oblong knobs, one on each side of 

 the beaks, which therefore terminate in a kind of gland. On the 



