TEREBRATULA. 17 



edge in adult specimens ; larger valve convex, with two shallow sinuses corresponding to 

 the biplications of the imperforated valve ; margin line slightly sinuated ; surface of valves 

 smooth, marked only by a few concentric lines of growth ; loop in smaller valve short, 

 attached only to the crura, and extending to about a third of the length of the valve ; 

 teeth of larger valve very strong, the posterior portion of the valve near the beak very 

 thick in adult shells ; structure punctuated ; length four inches two lines, width three 

 inches, depth two inches. 



Obs. On examining the figures given by Blumenbach in 1803, as well as those before 

 him, by Knorr and Walsh in 1756 and 1768, there seems to be little doubt that the shell 

 under notice belongs to the first named author's Terebratula grandis, these views being 

 likewise admitted by Professor Bronn and others; subsequently Schlotheim (1813) gave 

 to this shell the name of giganteus, while acknowledging it to be the same as Blumenbach's 

 species, referring to his work and figure. Baron von Buch adopts this last author's name, 

 giving as synonyms, T. bisinuata, Lamarck, and T. variabilis, Sow. (the figure of the spe- 

 cimens inserted in the Mem. de la Soc. Geol. de France are those of the Lamarckian species, 

 and not grandis of Blumenbach), but both Baron von Buch and Professor Bronn place under 

 the same name shells, in my opinion, quite distinct, such as T. bisinuata, Lam., Fragilis of 

 Kcenig, which certainly do not belong to the type of T. grandis ; the shell of T. bisinuata 

 being very thin and brittle, as Kcenig's name expresses, while that of the crag is very thick 

 and strong, besides differing by various other characters of shape. In 1829 it was described 

 and figured by Sowerby in the Min. Conch., under the name of T. variabilis, which name 

 has been in general use in England. Mr. Nyst (in 1843) rejects Mr. Sowerby's name, on 

 account of a similar denomination having been given by Schlotheim in 1813 to a plaited Lias 

 Terebratula, 1 and proposes in lieu that of T. Soiverbii. Mr. Charlesworth advocated likewise 

 in 1837, the name of T. maxima as a substitute for variabilis, but as we have stated above, we 

 cannot but believe it must be the same as that figured by Blumenbach in 1803 ; the figure 

 representing a large Terebratula measuring two inches nine lines in length, and two inches 

 one line in breadth, and in every respect identical in shape to many of our crag specimens, 

 which are, as Sowerby's name expresses, very variable in form, some being almost circular, 

 others oval, and even considerably elongated, convex, or depressed, regularly rounded, or with 

 a slight biplication in front. Mr. S. Wood having been able to trace specimens from less 

 than a line in length to the largest dimensions, much confusion has arisen from the desire 

 of some authors to combine, under one name, some strongly biplicated forms, such as 

 Ter. ampulla of Brocchi, T. bisinuata, and Pedemontana of Lamarck, thus extending 

 beyond reasonable limits the characters assignable to the type form. The best figures of 

 this species, as found in England, are those given by Mr. Charlesworth ; that author, 

 besides transcribing many interesting details on the species, adds that, " during the early 



1 Schlotheim's Ter. variabilis is a true Rhijnchonella, and therefore does not belong to the Terebratulae, 

 properly so called. 



