FOSSIL AND RECENT 123 



before ending in a slightly expanded maxillary head. Woodward (1907) suspected 

 the presence of only one supramaxilla, but the specimens are too imperfect to confirm 

 this suspicion. The teeth are unknown but a series of moderately large alveoli 

 set in a single row indicate a dentition unlike that of Osmeroides. The alveoli are 

 only weakly delimited from one another and in some parts of the bone the teeth appear 

 to have been set in a continuous groove. 



The quadrate/mandibular articulation occurs well behind the eye, beneath the 

 occiput. The mandible is deep throughout and a well-developed coronoid process 

 is absent. B.M.N.H. 49091 is the only specimen showing the dentition. At the 

 anterior end of the jaw the teeth are arranged in a band about four teeth wide. 

 Behind this level there is a single row of prominent alveoli in which were set somewhat 

 larger teeth. Lateral to this row of prominent teeth there are much smaller teeth, 

 while towards the anterior end of this series small alveoli indicate that there may have 

 been a medial row of very small teeth. The teeth are pointed. The absence of jaws 

 in the type specimen makes positive identification of this jaw (B.M.N.H. 49091) 

 difficult (Woodward 1907 only tentatively assigned this specimen to Dinelops). 

 However, the ornamentation upon the mandible is very similar to that of the 

 roofing bones. 



The post cranial skeleton is even more poorly known. There are approximately 

 14 rays in the pectoral fin which was held low down on the body. The dorsal fin 

 was situated above the pelvic fins and relatively far back. 



The scales are large, almost circular and marked only by fine circuli. A few 

 scales exhibit fine granulations in the posterior field. 



The characters of the skull roof and supraorbital agree with those of the Osmeroi- 

 didae. The jaws and dentition are, however, decidedly different and more advanced 

 than Osmeroides. Failing knowledge of the neurocranium, Dinelops is tentatively 

 retained in association with Osmeroides. 



Family PTEROTHRISSIDAE Gill, 1893 



Diagnosis. Albuloid fishes in which the snout is elongated ; mouth inferior. 

 Ethmoid commissure incomplete, running through premaxillae. Supraorbital 

 sensory canal not extending on to parietal. Occipital condyle formed entirely by 

 basioccipital. Interorbital septum membranous. Lateral ethmoid not sutured 

 to the parasphenoid, which is narrow. Parasphenoid and endopterygoid with 

 conical teeth opposed by a similar dentition upon the basihyal and basibranchial 

 tooth plates. Vomer edentulous. Premaxilla, maxilla and dentary with small, 

 needle-like teeth. Posterior infraorbitals narrow, incompletely covering the 

 cheek. Supraorbital small. Hyomandibular-metapterygoid foramen developed. 

 Premaxilla tightly bound to the mesethmoid ; maxilla moving independently ; a 

 single ovoid supramaxilla. Mandible with prominent coronoid process. Branchio- 

 stegals less than 10 in number. Gular plate absent. Dorsal fin elongated, anal fin 

 short based. Caudal skeleton with two or three uroneurals. Inner caudal rays of 



