82 Mr. T. R. Jones on Scandinavian Beyrichise. 



moulds of the interiors of these minute valves. The substance 

 of the valves being of the same thickness throughout, the in- 

 ternal casts represent with tolerable clearness the configuration 

 of the exterior. 



The Upper Silurian limestones of Gothland and the south of 

 Sweden often abound in minute, symmetrical, semicircular, tri- 

 lobed bodies, which are the heads and tails of little Trilobites of 

 the genus Agnostus (particularly A, pisiformis). Together with 

 these occur other somewhat similar trilobed forms, which how- 

 ever are smaller, longer in proportion, and not symmetrical. 

 These are Beijrichice. 



Drifted fragments of these fossiliferous Scandinavian lime- 

 stones occur abundantly in the sands and gravels of Mecklen- 

 burg, Brandenburg, and Pomerania ; and these blocks in their 

 weathered condition have yielded plentiful supplies of fossils to 

 the naturalists of North Germany. In 1769 C. F. Wilckens* 

 figured specimens of Agnostus pisiformis from this source, refer- 

 ring them with doubt to Trilobites (and proposing the removal 

 of Trilobites from amongst Mollusks to Insects). With these he 

 also figures a Beyrichia f {B. Wilckensiana, nobis), from Havel- 

 berg, without however arriving at any conclusion as to its true 

 nature. 



L. von Buch in his ' Recueil de Planches de Petrifactions re- 

 marquables},^ pi. 6, figures &ome Beyrichia in a limestone block 

 from near Giistrow in Mecklenburg, and regards them as the 

 young of his Leptcena lata, a view quite incompatible with every 

 character of these creatures, as M. Kloden has well explained in 

 his 'Die Versteinerungen der Mark Brandenburg §.' 



Kloden met with numerous specimens in weathered fragments 

 of the Scandinavian limestone from the gravels near Berlin ; and 

 he has given carefully executed (but evidently not quite correct) 

 figures of the valves of at least two species, in different stages of 

 growth, accompanied with a detailed description ||. This observer 

 remarked that these little fossils are not at all referable to the 

 heptmia which accompanies them, nor to any mollusk; and, 

 guided by the apparently symmetrical, semicircular, three-lobed 

 form of some of the specimens, he was led to regard them as 

 being probably the cephalic and caudal portions of the carapace 

 of small Trilobites, and to assign them to the genus Battus 

 { = Agnostus) y although he figures and describes the unsymme- 

 trical contour and irregular distribution of the surface-lobes of 



* Nachricht von seltenen Versteinerungen (8vo, Berlin), 1 769, pi. 7. f. 38. 



t Op. cit. p. 77- pi. 7. fig. 39. These specimens have been confounded 

 by Dalman, Kloden, Burmeister, &c., with the foregoing. 



X Fol. Berlin, 1831. These figures are too obscure for satisfactory re- 

 cognition as to their specific relations. 



§ Berlin, Bvo, 1834. i| Op. cit. pp. 112-119. 



