42 PROCEEDINGS OE THE GEOLOGICAL SOCIETY. [Apr. 6, 



Fossils of D 2, 3. Chemnitzia-grit. 



Chernnitzia procera, Deslong. J Sphserodus ; teeth. 



Nerinrea. j Squalus; teeth. 



Section III. — At Cold Comeoet. 

 A roadside excavation at Cold Comfort, made for extracting road- 

 material, has exposed a very rich upper bed of this zone. The 

 abundance and fine preservation in which the shells of Perna rugosa 

 are here found has obtained for this section the name of the " Perna- 

 bed," as this species has not yet been found in numbers in any other 

 locality in this district. 



It is probable likewise that the Perna-bed may represent a higher 

 portion of the Upper Trigonia-grit than that exposed at Leckhamp- 

 ton Hill. The reasons for this opinion are these: — It contains many 

 species of Oonckifera and Gasteropoda not found in the Trigonia-grit 

 of the latter locality ; moreover the Trigonia costata of the Perna- 

 bed belongs to a well-marked permanent variety of that species, 

 which has been designated by the name tenuicostata. 



ft. in. 

 A 1. Upper ragstone, consisting of hard fragments of 

 oolitic limestone, which form a coarse rubbly rock 



traversed by a fossiliferous layer 4 



A 2. The Perna-bed is a hard greyish mudstone, slightly 

 oolitic, and full of shells and of shelly fragments 

 in the form of crystallized carbonate of lime. It 

 breaks with an uneven and uncertain fracture .... 6 

 The Perna-bed rests upon a non- fossiliferous layer, which passes 

 into another band of rock covered with Serpulajlaccida, Goldf., on the 

 under side of the stone. 



ft. in. 

 A 3. A hard-grained oolitic limestone, the recently frac- 

 tured surface of which glistens with crystalline 

 particles or fragments of shells. The small portion 

 exposed is non-fossiliferous. This rock was 

 formerly extracted for road-material. Thickness 

 probably 8 



the shell ; it is equal to three-fifths of the length of the marginal carina, and 

 nearly twice as long as the lanceolate space ; the small lanceolate space is smooth 

 and flattened ; the marginal and inner carinas are delicate, without tubercles or 

 varices, and are only indented by the fine striations which cross the area and 

 pass over them. The costated portion of the shell is narrow, being only slightly 

 wider than the area ; and the general figure of the shell is very short, or truncated 

 posteriorly ; the umbones are not recurved, and the marginal carina is nearly 

 straight. 



Both species occur at Dundry ; and T. striata is, in the Inferior Oolite, the 

 prevailing representative of the genus throughout Somersetshire, Dorsetshire, and 

 in the Province of Calvados ; but it does not appear to have extended into the 

 Cotteswold sea, where the little group of species allied to T. striata is represented, 

 throughout all the beds of the formation, by T. formosa. The figure in the 

 'Petrefacta' of Groldfuss represents the characters of T. formosa less prominently 

 than the Cotteswold specimens. The figure of Quenstedt must be regarded as a 

 variety of T. formosa, with widely separated rows of costal ; and this is the 

 aspect which it assumes in the sands of the Upper Lias in Gloucestershire. — J. L. 



