CEPHALOPODA. 



89 



with a small central tube by radiating plates. 

 Island, Lake Huron. 



31 



3 sp. L. Silurian. Diiiiumoud 



Fig. 49. 

 Numerous examples of this 



Huronia vertebralis.* 



curious fossil were collected by Dr. Bigsby 

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

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

 many of the Artie expeditions. But ^ith the exception of one formerly in 

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

 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 cliffs, were 6 

 feet in length. 



5. Endoceras, Hall (Cono-tubulaiia Troost). Shell extremely elongated, 

 drical. Siphuncle very lai'ge, cylindi-ical, lateral ; thickened internally by re- 

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

 Lower Silurian, New York. 



6. Shell perforated by two distinct si2)huncles? 0. bisiphonatum Sby, 

 Caradoc sandstone, Brit. 



" Orthocerata \^^th tw^o siphuncles have been obsened, but there has 

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

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



Small orthocerata of vainous species, are frcqucnlly found in the body 

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

 parum and proteifonne of Hall, appear to be examples of tliis kind. 

 GoMPHOCERAS, J. Sby, 1839. 



Etym., gompkos, 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. Mas. by Captain Kellett and Lieutenant 

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



t Shells of Bellerophon and Jlurchisonia are found under the same circumstances. 



