SPIRIFER. 25 



of the upper lias, in the neighbourhood of Ilminster, and is found associated with Thecidea 

 rustica, Lept. Pearcei granulosa and a lingula, which was not sufficiently perfect to be 

 determined. 



Plate III, fig. 7, represents a specimen of natural size, from the collection of 

 Mr. Moore ; la is an enlarged illustration. 



19. Spirifer Walcotti, Sow. Plate III, figs. 2, 3. 



Spirifer Walcotti, Sow. 1823. Min. Con., vol. iv, p. 105, pi. 377, figs. 1, 2. 

 Terebratula — Desk. 1836. Nouv. ed. de Lamarck, vol. vii, p. 374. 

 Delthyris — V. Buck. 1840. Mem. Soc. Geol. de France, vol. iv, P re Sene, 



pi. 10, fig. 8. 

 Spirifer — Morris. Catalogue, 1843. 



— — Deslong champs. 1847. Soc. Lin. de Normandie. 



Trigonotrata — Bronn. 1847. Leth. Geog., pi. 18, fig. 14. 

 Spiriferina — D'Orb. 1849. Prodrome, vol. i, p. 221. 



Diagnosis. Shell inequivalved, variable, with elevated mesial fold, and four lateral 

 rounded plaits ; beak more or less recurved, area well defined, deltidium in two pieces, 

 hinge line shorter than the width of the shell ; surface punctuated and spinose ; spirals 

 and septum in the interior of both valves disposed as in Sp. rostratus. Dimensions vari- 

 able : length of the largest specimen known 19, width 24, depth 14 lines; but, in 

 general, the species does not attain that size. 



Obs. The species is easily distinguished from Sp. rostratus by its mesial fold, deep 

 sinus and plates. It was first discovered, many years ago, by Mr. Walcott, at Camerton, 

 about six miles from Bath, and represented by him in his work on petrifactions, fig. 33. 

 Sowerby also states that Mr. Walcott observed, of similar shells, " that those found on the 

 upper Bristol road, near Bath, are smaller, their shell thin, with a triangular hole between 

 the beak of the lower valve and the hinge, and have the body, fig. 33, a b, within them ; 

 it consists of two hollow cones, joined to each other by part of their basis, and to one of 

 the valves, but not so close as to prevent the animal, or part of it, from retreating into 

 them : their surfaces are beautifully covered with circular rows of small pyramids of spar." 

 Thus, as Mr. Sowerby observes, in vol. iv. p. 106, of his 'Min. Conch.,' Mr. Walcott 

 was the first discoverer of the spiral appendages, long before they were used as a generic 

 character ; he also observed the triangular fissure, but did not understand the nature of the 

 spirals or their use, and it is but just, in treating of this species, to state, that on it those 

 important calcareous appendages were first noticed. It is a very variable shell, as may be 

 seen in Plate III, figs. 2 and 3, is abundantly spread in the lower Lias, and more sparingly 

 in the middle Lias ; it is common near Radstock and Bath. Fig. 2 illustrates the largest 

 specimen which I have observed, and which was found there by Mr. Moore ; it is also met 

 with in France, in Burgundy, and in many other localities on the Continent. 



E 



