BELONOSTOMUS. 143 



1. Belonostomus cinctus, Agassiz. Plate XXX, figs. 1 — 7. 



1837-44. Belonostomus cinctus, L. Agassiz, Poiss. Foss., vol. ii, pt. ii, p. 142, pi. lxvi a, figs. 10 — 13. 



1850. Belonostomus cinctus, F. Dixon, Greol. Sussex, p. 367, pi. xxxv, figs. 3, 3*. 



1850. Belonostomus attenuatus, F. Dixon, ibid., p. 368, pi. xxxv, fig. 4. [Imperfect presymphysial 



bone; Brightou Museum.] 

 1888. Belonostomus cinctus, A. S. Woodward, Quart. Journ. Greol. Soc, vol. xliv, p. 145, pi. vii, figs. 



7—13. 

 1895. Belonostomus cinctus, A. S. Woodward, Catal. Foss. Fishes B. M., pt. iii, p. 438. 



Type. — Portion of squamation ; British Museum. 



Specific Characters. — Skull Avith very slender and slightly projecting rostrum, 

 probably not less than 24 cm. in total length. Mandible also very slender, the 

 presymphysial bone fifteen times as long as its maximum depth, keeled below, and 

 overlapping the mandibular symphysis in an oblique suture. External face of 

 rostrum and presymphysial bone sculptured with very fine longitudinal grooves, 

 with intervening ridges, which are more or less irregular. Large teeth of the 

 median series on the presymphysial bone, and those of the lateral series on the 

 rostrum, sharply conical and well spaced ; those on the splenial bone and some 

 other elements obtuse and mammillated. Scales of flank smooth, those of the dorsal 

 region marked with longitudinal rugae ; the scales of the lateral line truncated 

 inferiorly and much exceeding in depth the series below, those on the anterior 

 portion of the abdominal region being about four times as deep as broad. 



Description of Specimens. — This species is still represented in collections only 

 by fragments of the squamation and jaws. It is, however, definable, and the 

 greater part of its mandible at least is well known. The type specimen, a piece 

 of squamation in the Mantell Collection (No. 4266), is said to have been found in 

 association with the fragment of upper jaw and presymphysial bone which were 

 described with it by Agassiz. 



The imperfect upper and lower jaws of a small individual, in natural associa- 

 tion, are shown in PI. XXX, fig. 1 ; and the greater part of the rostrum of a 

 larger specimen is added in fig. 2. A very fragmentary piece of rostrum is also 

 represented by Agassiz in his fig. 10, loc. cit. As shown by these and other 

 specimens, the rostrum agrees with that of the typical Jurassic species of 

 Belonostomus in being hollow and consisting of one continuous piece of bone, 

 which is grooved along the middle of its oral face, and bears a single row of teeth 

 along each lateral margin. 1 The bone is gently rotund, not compressed to a sharp 

 ridge above, and fragments of it may thus be distinguished from those of the 

 presymphysial bone described below. Its outer face is sculptured with fine 

 grooves, which are mainly longitudinal, partly oblique; and the intervening ridges 

 are not enamelled. Its terminal portion, which seems to have been toothless and 



1 See especially Belonostomus dorsetensis, A. S. Woodward, Catal. Foss. Fishes B. M., pt. iii 

 (1895), p. 433, pi. xiv, fig. 2. 



