192 FOSSIL FISHES OF THE ENGLISH CHALK. 



contact with a [)ieco of cartilage alcove the remains of the pectoral arch {pcf.). 

 This spine is slender and straight, and, as shown l)y the broken section, it is 

 hollow for the greater part of its length, the internal cavity being especially large 

 in its lower half. It is round in cross-section, with the anterior margin pinched off 

 as a sharp keel. The rounded lateral face is nearly smooth, with some tendency 

 to a longitudinal ribbing, especially near the anterior keel. In the specimens 

 represented in figs. 4, 5, this ribbing is not conspicuous ; but in another fossil 

 (fig. 6), certainly referable to Elasmodectes and probably to E. wiUctti, it is so 

 strongly marked (fig. (5 a) as to have caused the spine to be mistaken for 

 Gd'lorlii/ncJms} The hinder margin of the spine is provided with a single longi- 

 tudinal series of smooth, downwardly-curved denticles, which are very close and 

 deeply overlapping (fig. 5), and extend to within a short distance of the base. 

 The apex of a spine with the hinder denticles apparently less crowded than usual, 

 is figured by Dixon, Greol. Sussex, pi. xxxii,* fig. 7. 



A few traces of the delicate calcified rings, which originally supported the 

 slime-canals, are seen on the head. 



Horizon and Localities. — Zone of Holastcr sulxjlobotms : neighbourhood of 

 Lewes, Glynde, and Amberley, Sussex ; Burliam, Kent. 



IGHTHYODOB ULITE8. 

 Genus C(ELORHYNCHUS, Agassiz. 



CcelorhyncJms, L. Agassiz (non Giorua, 1805), Poiss. Foss., vol. v, pt. i, 1844, p. 92. 

 CyJhidracanfJnis, J. Leidj, Proc. Acad. Nat. Sci. Pliilad., 1856, p. 12. 

 Ghjidorliynchus, M. Lericlie, Mem. Mus. Eoy. d'Hist. Nat. Belg., vol. iii, 1905, p. 159. 



Generic Characters. — Spine very long, slender, and gradually tapering, rounded 

 in section, and Avithout denticles; external surface longitudinally ridged and 

 grooved, each ridge corresponding to a wedge-shaped plate, which forms a small 

 sector of the spine. Central cavity relatively small, sometimes in part simple, 

 but divided by a median partition at least in the basal or proximal portion ; a 

 division-plane passing through the middle of the partition, thus allowing the spine 

 to be readily split into two symmetrical halves. 



Tii'pe Species. — GoelorJiynclius rectus (Agassiz, Poiss. Foss., vol. v, pt. i, 1844, 

 p. 92), from the Eocene of Europe. 



Uemarhs. — This fossil is commonly regarded as the rostrum of a Xiphioid 

 teleostean, and it bears some superficial resemblance to the rostrum of Blocliius, a 

 fish of uncertain relationships from the Upper Eocene of Monte Bolca, near 



' A.S.Woodward, " Ou the Fossil Fish-spiiies named Cwlorliynchvs, A^^nsmz,'' Ami. Mag. Nat. 

 Hist. [6], vol. ii (1888), p. 225. 



