1890.] UPPER CRETACEOUS FISHES. 633 



deep series of the flank is characterized in the abdominal and anterior 

 caudal region b) i prominent mesial vertical ridge, nearly correspond- 

 ing in position to the internal keel ; and the chief ornament consists 

 of irregular, thick, transverse rugae, which not only impart to the 

 ridge a nodular appearance, but also frequently pass into a series of 

 feeble crenulations at the hinder border. The dorsal and ventral 

 scales are similarly rugose, but more finely marked ; and in the 

 caudal region, too, there is a diminution in the prominence of the 

 ornament. 



Generic Determinatiori. — As already remarked, the species now 

 described was briefly noticed by Agassiz under the name of Aspido- 

 rhynchus comptoni. In 1841, as at the present time, the jaws were 

 undiscovered, and the most conspicuous character separating Aspido- 

 rhynchus from Belonostomus was thus not available for reference. 

 Two features now made known, however, appear to suffice for the 

 generic determination of the fish with absolute certainty. The sub- 

 orbital ring is in direct contact with the preoperculum throughout 

 its length, there being no supplementar3' cheek-plate, such as charac- 

 terizes Aspidorhynchus ^ ; and only two series of flank-scales are 

 deepened — one excessively so — while in Aspidorhynchus there are 

 invariably three such series, more nearly equal in their vertical 

 measurement". These being special characters oi Belonostomus, and 

 the Brazilian fish agreeing with the typical species of that genus 

 both in the arrangement and proportions of the fins and in the 

 development of the vertebral axis, there seems no reason to doubt the 

 generic determination here adopted. 



Specific Determination. — The Brazilian Cretaceous fish is the 

 largest species of Belonostomus of which any definite account has 

 hitherto been published. The fragmentary skull from the Cretaceous 

 of India, described under the name of Belonostomus (?) indicus ^, 

 ■will, if correctly determined, indicate even a slightly larger member 

 of the genus ; but the smoothness of the external bones readily sepa- 

 rates this form from the highly-ornate species now under considera- 

 tion. The large English Cretaceous species ' is also distinguished 

 from the Brazilian fish, among other points, by the feeble character 

 of its external ornamentation ; and the small associated species ° is 

 too imperfectly known for satisfactory comparison. The other 

 Cretaceous members of the genus, B. crassirostris ^ and B. lesind- 



' O. M. Eeis, " Ueber Belonostomus, Aspidorhi/tichtis, und ihre Beziehungen 

 zum lebenden Lcindostcus," SB. k. bay. Akad. Wiss., math.-uaturw. CI. 1887, 

 p. 173, pi. ii. fig. 7. 



^ B. Vetter, " Die Fische aus dem lithographischen Schiefer im Dresdener 

 Museum," Mitth. k. mmeral.-geol. Mus. Dresden, pt. iv. 1881, p. 89. 



^ Smith Woodward, "Description of a Fish-skull," Eec. Geol. Surv. India, 

 7ol. xxiii. (1890), p. 23. 



' Bdonostoiuus vincius, L. Agassiz, Poiss. Foss. vol. ii. pt. ii. (1843), p. 142, 

 pi. XTi. a. figs. 10-13 ; F. Dixon, Geol. Sussex, p. 367, pi. xxxv. figs. 3, 3* ; Smith 

 Woodward, Quart. Joum. Geol. Soc. vol. xliv. p. 145, pi. vii. figs. 7-13. 



« B. attemiatics, F. Dixon, Geol. Sussex (1850), p. 368, pi. xxxv. figs. 4, 4». 



" O. G. Costa, Paleont. Regno Napoli, pt. ii. (1856), p. 33, pi. ii. figs. 1, 2 

 (including B. grcwilis, Costa, ibid. p. 35, pi. ii. fig. 3). 



