VON BUCH ON BEAR ISLAND. 57 



Spirifer Capensis. It is more than two inches broad, and be- 

 longs to the division of the Ostiolati, with perfectly smooth sinus ; 

 and among these to the subdivision of the Spirifer speciosus. The 

 lateral ribs are much rounded and broad ; hence only eight or nine 

 ribs cover each side. The smus is remarkably narrow and confined, 

 as is common in the Spirifers whose hinge-border is broader than the 

 valve. Its proportion to the whole breadth is as 17 : 100. The 

 striee of growth do not appear very distinct. 



The most similar of all the species of Spirifers hitherto known is 

 found in the Spiti valley in Thibet, on the northern declivity of the 

 Himalaya. It was brought thence by the well-known Dr. Gerard to 

 Calcutta, and has been well-figured, though without a name, by 

 Hamilton Royle in his large botanical work. In this species, how- 

 ever, the strise of growth project like scales. 



On the Khine also, not far from Ems, there are found lying between 

 the casts, so remarkably numerous, of Spirifer speciosus var. mi- 

 cr opt era, other casts with divided ribs, and also only six on each side 

 of the sinus. They are greatly broader than long ; but for closer 

 determination more perfect specimens are still desirable. 



On the whole, however, it is very remarkable how species of Spi- 

 rifers with divided ribs are far more peculiar to the Productus, or 

 carboniferous formation, than to the older Devonian, or still more, the 

 Silurian strata. From the latter not even a single species is known 

 which has the smallest similarity with the Spirifers of Bear Island 

 or of Van Diemen's Land. If dichotomy appears anywhere on the 

 valves, it is only on the border of the sinus, and not on the sides. 

 Spirifer dorsatus (His. Lethsea Suec. t. 21. f. 14) from the Silurian 

 beds of the island of Gothland, which might perhaps be regarded as 

 an exception, belongs to the Terebratula, and is not distinct from 

 Terebratula borealis, Schl. 



This law of the distribution of the species of Spirifers in the various 

 older and newer formations appears very distinctly when we subject 

 the species with divided ribs to a more accurate review. The more 

 important, and those best known, are the following : — 



1 . Spirifer Keilhavii, in the Productus sandstone of Bear Island. 



2. Sp. pectino'ides, De Koninck, pi. 16. fig. 4 {dichotomus^QoXdi- 



fuss), in the carboniferous limestone of Vise and of Batingen, 

 with finer ribs in the sinus. 



3. Sp. recurvatus, De Koninck, from Vise, many fine ribs, divided 



on the border, in the sinus also, pi. 16. fig. 5. 



4. Sp. laxus, Portlock, Geol. of Londonderry, pi. 37. fig. 6. "With 



smooth sinus, four or five broad ribs on each side, which towards 

 the border divide very wide and open. From the carboniferous 

 sandstone of Fermanagh. 



5. Sp. furcatus, M'-Coy in Griffith Ireland, pi. 22. fig. 12. 



Finer ribs in the sinus ; five divided ribs on each side. It 

 ought scarcely to be distinguished from the Sp. pectino'ides. 

 In the Irish carboniferous limestone. 



6. Sp. Strangwaysi, De Verneuil, Murch, Russia, vol. ii. pi. 6. fig. 1 . 



Very like the Sp. trigonalis, the ribs of which, however, do 

 not dichotomize. Even in this species only a few^ of the lateral 



