CRANIAL OSTEOLO&T OP THE OSTEOGLOSSIDJS. 257 



under consideration tliere are ten only, but the series is probably 

 incomplete *. 



The first seven have the form of curved thin rods, the last 

 three are larger and broader. The first eight are connected with 

 the outer surface of the ceratohyal, the other two with the outer 

 surface of the epihyal. 



Hyohranchial Series. — The hypohyal is single on each side, 

 4nd is attached to the upper half of the anterior extremity of 

 the ceratohyal. The anterior end of the urohyal lies between the 

 lower halves of the anterior ends of the right and ]eft cerato- 

 hyals. The urohyal is comparatively small, and does not extend 

 back behind the middle of the second basibranchial. A large 

 dentigerous bone overlies the glossohyal cartilage, the first and 

 second basibranchial bone^', and the anterior half of the third. 

 !Prom the mesial edge of the ventral side of the anterior end of 

 the second hypobrauchial there descends a stout process of rod- 

 like form, almost equalling in length the hypobrauchial itself. 

 Tlie first pharyngobranchial is cartilaginous and there is no 

 spicular bone. 



OSTEOGLOSSUM BICIRRHOSIIM. 



The skull examined is that belonging to a skeleton in the 

 Eritish Museum, labelled " 1890.2.25.60, Brazil." 



The frontal bones are longer than in Osteoglossum LeicJiardti, 

 and the nasals are shorter, while the mesethmoid is quite dimi- 

 nutive. The prefi'ontals appear to be unossified. The posterior 

 temporal fossa does not open into the lateral temporal groove. 

 The ascending wing of the parasphenoid enters into relation with 

 the postfrontal, as in Osteoglossum for mo sum (Bridge, I. c. p. 302). 

 The dentition, as a whole, is less robust than that of O. LeicharcUi, 

 and the clump of teeth on the parasphenoid is smaller. The 

 ventral surface of the anterior half of the parasphenoid is strongly 

 grooved, whereas in 0. Leichardti it is flat. 



There is a distinct third, or supra temporal, limb to the post- 

 temporal, whereas in O. Leichardti this is barely recognisable. 

 The opening by which the sensory canal comes to the surface of 

 the preopercular bone occurs higher up that bone in Osteoglossum 

 hicirrJiosum than in 0. Leichardti. The premaxilla bears 10 or 

 11 teeth, and the maxilla, which is conspicuously longer and 

 more slender than that of O. Leichardti, carries 64 to 68 teeth. 



* In another specimen (No. 92.1.14.37) there are 13 rays. 

 LINN. JOUKN. ZOOLOGY, VOL. XXIX. 18 



