CEPHALOPODA. 



with a small central tube by radiating plates. 3 sp. L. Silurian. Drummond 

 Island, Lake Huron, 



l\ 



Fig. 49. Huronia verfebralis.* 



Numerous examples of this curious fossil were collected by Dr. Bigsby 

 (in 1822), and by the officers of the regiments formerly stationed on Drum- 

 mond Island. Specimens have also been brought home by the officers of 

 many of the Artie expeditions. But with the exception of one formerly in 

 the possession of Lieut. Gibson, 68., and another in the cabinet of Mr. 

 Stokes, the siphuncle only is preserved, and not a trace remains of septa or 

 shell wall. Some of those seen by Dr. Bigsby in the limestone cliff's, were 6 

 feet in length. 



5. Endoceras, Hall (Cono-tubularia Troost}. Shell extremely elongated, 

 drical. Siphuncle very large, cylindrical, lateral ; thickened internally by re- 

 peated layers of shell, or partitioned off by funnel-shaped diaphragms. 12 sp. 

 Lower Silurian, New York. 



6. Shell perforated by two distinct siphuncles? 0. bisiphonatum Sby, 

 Caradoc saridstone, Brit. 



" Orthocerata with two siphuncles have been observed, but there has 

 always appeared something doubtful about them. In the present instance, 

 however, this structure cannot be questioned." (J. Sowerby.) 



Small orthocerata of various species, are frequenlly found in the body 

 chamber and open siphuncle of large specimens.! The endoceras gemelli- 

 parum and proleiforme of Hall, appear to be examples of this kind. 

 GOMPHOCERAS, J. Sby, 1839. 



Etym., gomphos, a club, and ceras, a horn. 



* Fig. 49. Huronia vertebralis, Stokes, a, from a specimen in the Brit. M., presented 

 by Dr. Bigsby. The septa are added from Dr. Bigsby's drawing ; they were only in- 

 dicated in the specimen by "colourless lines on the brown limestone," b. represents 

 a weathered section, presented to the Brit. Mus. by Captain Kellett and Lieutenant 

 Wood of H.M.S. Pandora. The figures are reduced . 



t Shells of Seller ophon and Ai urchisonia are found under the same circumstances. 



