ANIMALS. 109 



The foregoing diagnosis is given — not because those pubhshed by Von Buch and 

 Geinitz are imperfect — but simply, in consequence of a wish to describe this remarkably 

 variable and interesting species as it occurs in England. 



In the German specimens of Sireptorhynchus pelargonatus, the umbone appears to be 

 generally more incurved than in those found in this country, nearly all the latter I have 

 seen having the umbonal point turned up, though not so much as it is in the specimen 

 in PL X, figs. 21,22. Concluding from the figures in the ' Versteinerungen,' this 

 species appears to have attained a larger size in Germany than in England ; but I have 

 lately procured at Tunstall Hill a fine specimen, much larger than any figured in this 

 Monograph, though not quite so large as those represented by Dr. Geinitz. The 

 irregularly twisted character of its beak is well displayed in the specimens represented 

 by figs. 23, 27. Both valves are beautifully marked with slight dichotomous ridges, 

 radiating from the umbonal point, and curving round to the hinge line in the cardino- 

 lateral regions, as characteristic of De Verneuil's group Arcuato-striata. The dental 

 plates, represented in fig. 28 a^ are in the form of slightly-raised, obtusely-rounded 

 ridges ; the socket plates {b) are rather large, and they project divergingly into the 

 cavity of the shell ; and the boss, which is bilobed and erect, occupies the inferior 

 half of the fissure between the dental plates. The shell has a punctated structure ; as 

 I have seen specimens, in the state of casts, exhibiting here and there numerous minute 

 points, evidently casts of minute tubular perforations, and resembling, though on a 

 smaller scale, what undoubtedly are casts of the latter in Trigonotreta cristata, hereafter 

 to be noticed. The tubular perforations, or rather their casts, are larger in the umbonal 

 region than in other places. 



Streptorhynchus pelargonatus bears a striking resemblance to a fossil described by 

 Dr. Braun, in Count Miinster's ' Beitrage,' Heft iv, pi. ix, figs. 3 a, b, c, under the name 

 oi Spirifer spurius : it occurs in the {}) Trias Marls of St. Kassian ; and is evidently 

 closely allied to, and congeneric with, the present species. 



The present species was described first by Baron Schlotheim, in the ' Denkschriften 

 der Koniglichen Akademie der Wissenschaften zu Miinchen,' in which are several 

 unmistakable figures of it. The so-called Spirifer minutus noticed in Professor Sedgwick's 

 paper, as occurring at Humbleton Hill, is, I strongly suspect, the same shell, since 

 impressions of the latter, which might readily be supposed to belong to a minute 

 Spirifer, occur occasionally in this locality. M. von Buch, describing the same species 

 under the name of Orthis Laspii, in 1834, states that it W8S discovered by M. Laspe at 



1 10 au bord. La plus grande largeur est au dessous du milieu de la longueur. Longueur, 100 ; largeur, 109; 

 hauteur, 70 ; largeur du sinus, 078 de la largeur totale ; largeur de I'area, 0'G3." (Essaid'une Classification 

 et d'une Description des Delthyris ou Spirifers et Orthis, par Leopold de Buch. Translated par Henri 

 le Cocq, Mem. Soc. Geol. de France, tom. iv, pp. 210-11, 1840.) 



1 The internal parts of the specimen represented in pi. x, fig. 28, appear larger than they really are, in 

 consequence of being incrusted with particles of foreign matter. 



