CEICK : CEPHALOPOD FROM THE LONDON CLAY. 257 



depressed, and bears throughout its length a median, broad, shallow, 

 feebly-marked groove. There are twenty-five sutures, their distance 

 apart ranging from 2 mm. on the anterior portion of the specimen 

 to 0-5 mm. on the posterior part; on the sides they are very 

 slightly oblique, sloping towards the ventral surface, and in the 

 middle of this surface each has a very small V-shaped lobe. The 

 specimen has been broken across; it is partly hollow, and, so far 

 as one can see, exhibits no signs of septa or siphuncle. On the 

 ventral surface there are two patches of an outer covering, each of 

 ■which, the anterior one especially, appears to consist of two layers, an 

 inner thin and fairly dense layer, and an outer one which is much 

 less dense and only partially preserved, the fragments that are left 

 having a coarse fibrous appearance, the fibres being arranged 

 longitudinally. The outer layer seems to have had a strong median 

 ridge, portions of this being preserved on each patch, along the 

 median line of the ventral surface. This ridge is 15 mm. wide on 

 the anterior patch, and about 1 mm. wide on the posterior one ; it is 

 ill-defined laterally, and may therefore be only a portion of a much 

 wider ridge which occupied the median line of this surface. 



So far as I am aware, the only clibranchiate Cephalopod hitherto 

 recorded from the London Clay of Sheppey is Belosepia sepioidea, 

 Blainville, 1 but the present specimen cannot be a cast of the posterior 

 cavity of that form, because its apical angle is too small, and the 

 cavity, which is represented by this natural cast, is much too deep and 

 too large. The affinities of the present specimen seem, however, to be 

 with the genus Beloptera, Blainville. 3 In this genus the rostrum 

 only is known, consisting of two conical portions, the anterior one 

 hollow and the posterior one solid, joined together by their apices and 

 connected by two more or less salient lateral expansions. The species 

 of this genus fall into two sections : one includes those forms in which 

 the lateral expansions are well developed and constitutes the genus 

 Beloptera {sensu stricto) ; the other comprises the forms in which the 

 lateral expansions are quite rudimentary or, according to some authors, 

 absent, and constitutes the subgenus Belopterina of Munier-Chalmas. 3 

 In Beloptera (sens, str.) the anterior conical portion of the rostrum 

 usually bears on its ventral surface two more or less prominent ridges, 

 one on each side of the median line, whereas in Belopterina there is 

 a single median well-developed ridge. In some of the examples of 

 Beloptera belemnoidca i (or belemnitoidea 5 ) in the British Museum 

 collection, particularly in the example figured by J. de C. Sowerby 6 



1 De Blainville: Man. Malacologie, 1825, p. 622, Atlas (1827), pi. xi, fig. 7. See 



also K. B. Newton & G. F. Harris : Proc. Malac. Soc., vol. i, pt. 3 (June, 

 1894), p. 120. 



2 De Blainville : Man. Malacologie, 1825, pp. 621, 622 ; and Mem. Belemnites, 1827, 



p. 111. See also R. B. Newton & G. F. Harris: Proc. Malac. Soc, vol. i, 

 pt. 3 (June, 1894), p. 122. 



3 Bull. Soc. geol. France, ser. n, torn, xxix (1872), p. 531. 



4 De Blainville: Mau. Malacologie, 1825, p. 622, Atlas (1827), pi. xi, fig. 8. 

 a De Blainville: Mem. Belemnites, 1827, p. ill, pi. i, fig. 3. 



6 J. de C. Sowerby: Min. Conch., vol. vi, p. 183 (1828), pi. i>xci, fig. 3. 



