BELEMNITES OF THE LIAS. 37 



Proportions. The longest diameter at the apex of the phragmocone being taken at 

 100, the ventral part is 46, and the dorsal part 54 ; the axis of the guard 160. 



Phragmocone. Quite straight, with a slightly oval section, ending in a spherule ; 

 sides indined 21°, ventro-dorsal inclination 23°. Septal diameter seven times the depth ; 

 axis of the phragmocone half as long as the axis of the guard ; alveolar cavity three 

 times as long as the axis of the guard. 



Observations. The substance of the guard is usually a clear, brown, calcareous spar, 

 with large radiating pencils of fibres. In some specimens the striations near the apex 

 gather into interrupted longitudinal plaits, especially on the dorsal aspect. In one case 

 the whole surface is marked by little ridgy swellings ; in others quite smooth, except near 

 the apex. 



Among foreign specimens from Mokon, near Mezieres, mostly referred by M. Hebert 

 to .5. brevis, var. b, Blainville, I have seen some which have the essential characters above 

 assigned, though generally somewhat compressed. Among them one or two may be 

 chosen which fairly match our English examples. Specimens of Lias Belemnites are 

 occasionally seen in foreign museums bearing the names of B. brevirostris, D'Orb. (also 

 called B. curtus on plate x, figs. 1 — 6, of this author's ' Terr. Jurassiques,' and B. rostri- 

 formis (Qu.), which come near to our specimens. The former is known to me by many 

 examples, all of which are straight; the latter is a somewhat oblique, not arched, very 

 short, compressed Belemnite, with acro-lateral grooves, and is ranked among the Belemnites 

 tripartiti by Quenstedt. It seems, therefore, that a new designation is necessary for 

 this not common fossil, for which the only synonym I can suggest is B. brevis, var. b, in 

 part, of Blainville. It is not identical with what Prof. Morris mentions as B. brevirostris 

 from near Cheltenham. 



Locality. In Lower Lias, near Bristol, with Amrn, Turneri [Stoddart) ; Lyme Regis 

 and Bath {Phillips). Foot of Black Venn, Lyme Regis, with^. Bucklandi {Bay). 



Belemnites excavatcjs, n. s. PI. 11, fig. 4. 



Beference. Buckland, ' Biidgewater Treatise/ p. 70, pi. xliv', fig. 14, 1836, where it is 

 called B. brevis (?), a name previously employed for a very difierent species by Blainville. 



Guard. Rapidly tapering to a blunt end, with obscure lateral furrows. The axis 

 excessively short. Sections show the substance of the guard everywhere nearly of equal 

 thickness, like the finger of a thick leather glove. 



Proportions. The diameter, v d, being taken at 100, the axis is of unexampled short- 

 ness — less than 100 ; thus in form somewhat reminding us oi Acanthoteuthis, though its 

 texture is of the ordinary kind ; transverse diameter less than the ventro-dorsal diametei-, 

 especially toward the apex. 



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