U4 ELOPIFORM FISHES 



plate and an elongate basibranchial plate representing the compound plate asso- 

 ciated with the first three basibranchials. The teeth borne by these plates are small, 

 set in shallow sockets and range in shape from conical to hemispherical. On the 

 basibranchial plate the teeth situated anteriorly are slightly larger than those 

 posteriorly. 



The cerato- and epibranchials are long, thin, and bear a deep groove upon the 

 lateral face for the branchial arteries. The medial surface of these elements is 

 smooth and the associated tooth plates lay free in the dermis. The tooth plates are 

 oval in shape and bear villiform teeth. Somewhat larger tooth plates may be 

 identified as infrapharyngobrancial tooth plates (upper pharyngeals of Nelson 

 1969a). The teeth borne by the upper pharyngeals are smaller than those on the 

 basibranchial tooth plates. 



Postcranial skeleton. What little is known of the postcranial skeleton is very like 

 0. lewesiensis. The squamation is similar to that of the type-species but, as may be 

 expected in a smaller fish, the scales show much less ornamentation. 



Osmeroides latifrons Woodward 



(Text-figs. 55-59) 



1907 Osmeroides latifrons Woodward : 119, pi. 24, figs. 1, 2, 3. 



Diagnosis (emended). Species known only from the cranium and anterior part 

 of trunk. Length of cranial roof less than twice the maximum width, at the 

 sphenotic level. Parietals broader than long. Frontals becoming narrow above 

 lateral ethmoids. Dermal cranial bones smooth, marked only by fine radiating 

 growth lines. Interorbital septum absent or membranous. Parasphenoid reaching 

 rear of neurocranium. Quadrate/mandibular articulation beneath lateral ethmoid. 

 Branchiostegal rays less than 15 in number. Scales large, exposed area marked 

 by a fine reticulation of rugae. Anterior field of scales without radii. 



Holotype. B.M.N.H. P. 10465, exhibiting skull roof, from the Upper Cenomanian 

 of Kent, S.E. England. 



Material. In addition to the type, B.M.N.H. specimens P.5679, P.9699, P.10466 

 and P. 1 1 190 were examined. The last-mentioned specimen was prepared in acetic 

 acid. All specimens are from the Upper Cenomanian of Kent, S.E. England. 



This species is known only by imperfect cranial remains and the anterior region 

 of the trunk. The account of the cranium is based mainly on B.M.N.H. P.11190. 



Description. Osmeroides latifrons differs considerably from other species of 

 Osmeroides. Many of the observable differences are features in which 0. latifrons 

 resembles the Albulidae and Pterothrissidae. However, a basic similarity in neuro- 

 cranial structure and the retention of several primitive features justify the inclusion 

 of this form within the genus Osmeroides. The description given below is designed 

 to illustrate the differences between 0. latifrons and the type-species, 0. lewesiensis. 



Neurocranium. The cranial bones are unornamented, except for a few lines of 

 growth on the frontal, infraorbitals and operculum. Comparing the neurocranial 



