422 Mr ANSTED, ON A NEW GENUS, &c. 



merest thread, which can no longer be capable of performing any office 

 in the animal economy. 



As an extreme instance of this, I would refer to the fossil represented 

 in Plate VIII., Figs. 5, 6. It is in extremely good preservation, but 

 does not show the slightest appearance of a siphuncle on the dorsal 

 margin, or elsewhere, although it resembles in some respects one of 

 Count Minister's goniatites, named G. subsulcatus. I have had it 

 figured, because it shows very beautifully the singular extent to which 

 the envelopement of one whorl by the rest is sometimes carried, and 

 the marked resemblance which the specimen bears to some of the mi- 

 croscopic genera of D'Orbigny's Foraminifera. Its shape is lenticular, 

 and it measures more than three-quarters of an inch across. In the 

 absence of better information, I am compelled to call it a goniatite, 

 but I cannot help thinking, that for this and many other species also 

 doubtful, it may be found necessary to establish a separate group, 

 founded on the almost total absence of the siphuncle. 



In conclusion, I would observe, that among the known, but as yet 

 undescribed fossils of the Silurian System, there is no instance of any 

 species referrible to our new genus ; and thus we have another instance 

 of the wide separation denoted even by the zoological character 

 of these ancient formations, which are indeed sufficiently distinct by 

 the known occurrence of intervening deposits. It is the opinion of 

 Professor Sedgwick, that these Cornish rocks, which contain the organic 

 remains described, are the lowest fossiliferous rocks of Devonshire and 

 Cornwall, and far, very far removed in the order of their deposit from 

 the mountain limestone, with which it has been attempted to identify 

 them. 



D. T. ANSTED. 



Jesus College, 



18th May, 1838. 



