NEWTON AND HAEEIS : BRITISH EOCENE CEPHALOPODA. 125 



hj removal of a thin projecting part of the rostrum, consequent on 

 the rolling action. The absence of an elongated rostrum may be 

 similarly accounted for; indeed indications of its former presence 

 are not wanting, some traces of its structure remaining on the smooth 

 posterior extremity of the specimen. 



We have, therefore, ventured to restore Belemnosis as represented 

 in the annexed figure {B). It now presents considerable analogy with 

 the genera Beloptera and Spiridirostra^ but the former is characterised 

 by a well-developed ventral paries, which is practically absent in 

 our specimen. It agrees in most respects with the latter genus, 

 in which the ventral paries is also very thin. The chambered shell in 

 Spirulirostra has a considerable initial curvature, much greater than 

 in Beloptera ; and although the first few chambers are removed, 

 according to our view, in the so-called Belemnosis, it seems clear 

 from the disposition of the existing chambers that the shell had 

 a greater curvature than that of Beloptera. Another point of 

 similarity with Spiridirostra is the disposition of the septa, which 

 are practically at right angles with the axis. We have no hesitation, 

 therefore, in regarding Belemnosis, Edwards, as synonymous with the 

 earlier Spirulirostra, D'Orbigny. 



This conclusion is interesting from more than one point of view — 

 (1) it removes an apparent anomaly, by accounting for the presence of 

 this supposed ventral aperture, the function of which was certainly 

 an enigma; (2) it enlarges the range in time of S2nrulirostra, which 

 has hitherto only been known to occur in the Miocene beds (Helvetian) 

 of Northern Italy, whereas our specimen belongs to the Lower Eocene 

 (London Clay) ; and (3) it adds another species to that genus, of 

 which only one {S. Bellardii) has up to the present time been re- 

 corded, so far as we are aware. 



SpiEtrLrROSTEA ANOMAiA, J. de C. Sowerby. 



Beloptera anomala, J. de C. Sby. — Mineral Conchology, 1828, vol. vi. 



p. 184, pL 591, fig. 2. 

 Belemnosis plicata, Edw. — Mon. Pal. Soc. 1849, p. 40, pi. ii. figs, 



3a^3e. 

 Belemnopsis anomala, J. E. Gray. — Cat. Moll. British Museum Ceph. 



Antepedia," 1849, p. 158. 

 Belemnosis anomala, K. B. Is^ewton. — Syst. List Edwards Coll. British 



Museum, 1891, p. 289. 



This species differs from the type of the genus in that the later 

 chambers of the shell are much more expanded, whilst its dorsal 

 paries is veiy thick and keeled. Judging from D'Orbigny's figures 

 of S. Bellardii it would appear as though the ventral paries of our 

 specimen is thinner, whilst the contiguous outer sheath is slightly 

 inflated and plicated. Mr. Edwards does not explain why he changed 

 Sowerby' s name for the species, and there seems no reason for so 

 doing. Only one specimen known. Length, 13 mm. 



Formation. — London Clay. Locality. — Highgate Archway. 



