BELEMNITES OF THE LIAS. 39 



Belemnites dens, Simpson. PI. II, fig. 6. 



Reference. Belemnites dens, Simpson, 'Fossils of the Lias of Yorkshire,' 1855 

 (no figure). 



GuAKD. " Length of guard not twice its width, much depressed, sides straight ; 

 finely striated longitudinally, or corrugated and roughened most towards the blunt apex, 

 with small tubercles. Some are longer in proportion." 



Locality. " Lower Lias, Robin Hood's Bay, Yorkshire." 



The above is the published description of the curious fossil of which I here present a 

 sketch, in hopes of being able to add more details hereafter. I have seen only one 

 specimen, which is in the Whitby Museum. The striations are like those seen on other 

 Belemnites, as B. elongatus, and are original marks of structure left by the secreting 

 membrane, or periostracum, not the efiect of decomposition, as in B. acuarius macer of 

 Quenstedt C Cephalop.,' pi. xxv, figs. 27, 28, 29). 



Belemnites clavatus, Blainville. PL III, fig. 7. 



Beference. B. clavatus, Blainville, p. 97, pi. iii, fig. 12, 1827. 



B. pistilliformis. Sow., ' Min. Conch.,' p. 117, t. 589, fig. 3, 1828. 

 B. clavatus, Quenstedt, ' Cephal.,' p. 398, t. xxiii, fig. 19, 1849. 

 B. clavatus, D'Orb., 'Pal. Fr. Terr. Jurass.,'" p. 103, t. xi, figs. 19 — 23, 

 1842. 



Guard. "Very elongate, fusiform, contracted in all the region about the alveolar apex, 

 evenly swollen between this and the apex, which is pointed. On the lateral faces of the 

 contracted parts of the sheath are traces, more or less distinct, of two longitudinal furrows, 

 which cease on the expanded posterior part, and do not approach the apex. 



Sections show the guard to be composed, where it covers the phragmocone, and 

 for a certain space behind the alveolar cavity, of pale, perishable, longitudinal laminae, 

 which accounts for the frequent absence of those parts, and the production of the form of 

 Actinocamax, Mill. Transverse sections nearly circular, with traces of the grooves about 

 the alveolar region. With age, the whole figure becomes more lanceolate, and thickens 

 over the alveolar region. 



Extreme length observed, 4 inches. 



Proportions. The axis, in ordinary (middle-aged ?) specimens, is from five to ten 

 times as long as the diameter at the alveolar apex. It is nearer to the ventral side ; in 

 some specimens very much so, in others very little. 



Phragmocone. In a specimen discovered by Mr. Day at Lyme Regis (PI. II, fig. 7, s) 



