462 DR. W. G. RIDEWOOD ON THE CRANIAL [DeC. 13, 



upper, and a long tapering bone lying antero-dorsally to the orbit. 

 The gape is small, and its upper margin is formed almost entirely 

 by the premaxillse, although these are small bones, while the 

 maxillae are large. A single row of minute teeth occurs along 

 the edge of the premaxilla, and these are met by a similar row 

 along the sharp front edge of the dentary. The ventral edge of 

 the maxilla is provided with a single row of teeth, but, as in 

 Gluj^ea, these do not bite against any mandibular teeth. There 

 are two surmaxillfe above each maxilla. 



The angular bone is distinct from the articular. The ventral 

 surfaces of the palatine and entopterygoid bones are extensively 

 covered with minute teeth ; there ai-e no teeth on the vomer. 

 The subopercular is reduced in size ; the branchiostegal rays are 

 five or six in number on each side. A spicular bone is present, 

 and has the form of an upright rod which broadens out at its 

 lower end. 



Hyperlophus copii. 



The genus BiplomysUis was established by Cope in 1877 (Bull. 

 U.S. Geol. Geog. Surv. Territ. iii. 1877, p. 808) for certain 

 extinct species of fish allied to Clupea, but difiering in the 

 possession of "a series of dorsal scuta, which extend from the 

 supraoccipital region to the base of the dorsal fin." The genus 

 has since been found to be represented at the present day by 

 species living in the rivers of New South Wales and Chili. 



The generic name Diplomystus is, I understand fi'om Mr. Bou- 

 lenger, preoccupied by a Siluroid fish, or, to be more exact, the 

 name of this Siluroid [Diplomyste, Dumeril ; Di^ylomystes, Bleeker ; 

 Diplomystax, Giinther) so closely resembles the name Diplomystus 

 as to render the latter invalid. In such case the wisest plan is 

 to apply to " Herrings with occipito- dorsal sei-rature" the name 

 Hyperlophus, as suggested by Ogilby in 1892 (Rec. Austral. Mus. 

 ii. 1892, p. 26). 



The specimen examined is one in the British Museum Collec- 

 tion, prepared from a fish about 3| inches in length, and marked 

 '' Hyperlophtis copii, 97.10.27.38, N. S. Wales, Ogilby." 



The parietal bones are separated ; the temjjoral grooves are 

 as in Clupea; a temporal foramen is present and an auditory 

 fenestra. The pre-epiotic fossa is present, but with the exception 

 of its vipper part it is largely obliterated by the bulging of the 

 squamosal bulla. The vesicle of the swim-bladder in the pro-otic 

 bone is large, and its bony envelope projects upon the ventro- 

 lateral face of the pro-otic. The opisthotic is small ; the basi- 

 sphenoid cannot be recognised in the specimen under consideration ; 

 the orbitosphenoid extends forward to meet the prefrontals. 

 There are right and left posterior wings of the parasphenoid, 

 and the eye-muscle canal opens between them. 



The post-temporal has a,n epiotic and an opisthotic limb, but 

 no supratemporal limb. The supratemporal is triradiate, and the 

 ray which passes to the parietal is longer than the other two. 



