8 BRITISH OOLITIC AND LIASIC BRACHIPODA. 



possible to mention all the authors who have alluded to certain known species without 

 figuring or describing them. Many errors have been committed, and much confusion pro- 

 duced, by the rapid manner in which some authors have determined their species ; we will 

 not, therefore, refer to those which are published simply under the form of lists. 1 



Genus — Lingula, Bruguiere. 1789. 



Shell inequivalved, one valve more convex than the other, more or less oval, elongated, 

 tapering and pointed at the beaks, widened at its palleal region, without hinge, valves 

 held together by the adductor muscles ; attached to submarine bodies by a long muscular 

 peduncle issuing from between the beaks, a groove existing for its passage in that of larger 

 valves ; arms fleshy, without any shelly support ; structure horny, covered by an epidermis ; 

 two muscular impressions on the one, four on the other valve.* 



Obs. We are only acquainted with one authentic species of British Oolitic Lingula, 

 L. Beanii. Sowerby mentions another, L. ovalis, as from Kimmeridge clay, but which 

 appears to belong to the lower green sand. It is worthy of remark, that the genus Lingula, 

 one of the oldest created forms, has persisted, with very little variation in shape, up to the 

 present day, a circumstance very unusual among the Brachiopoda. 



1. Lingula Beanii, Phillips. Plate I, figs. 1, la, lb, 1c, Id. 



Lingula Beanii, Phillips. 1829. Geol. of Yorksh., Part i, pi. 2, fig. 26. 



— — Morris. 1843. Catalogue, p. 122. 



— — Bav. 1847. Lond. Geol. Journal, vol. i, pi. 18, figs. 26—30. 



— — Bronn. 1849. Index Palseontologicus, p. 655. 

 „ _ B'Orb. 1849. Prodrome, vol. i, p. 286. 



Diagnosis. Shell irregularly oblong, oval, rounded in front ; valves thin, convex, with 

 numerous concentric lines of growth ; internal muscular impressions strongly marked. 

 Dimensions variable; average size 10 lines long by 6 broad. 



Obs. Professor Phillips was the first to notice this species in his work on the ' Geology 

 of Yorkshire,' but gives no further description than that it approaches Ling, mytiloides of 

 Sowerby. From the great resemblance various species of Lingula bear to each other, it is 



1 From the necessity of bringing out the work in parts, and from the strong aversion we have to the 

 objectionable practice of giving lists of new species before they are described and figured, we cannot here 

 give the tables and general conclusions as to the distribution of tbe various species till the conclusion of the 

 series of Monographs on these subjects. 



2 For more ample details, see general Introduction. 



