1904.] OSTEOLOGY OF CLUPEOID FISHES. 463 



The uprig-lit and horizontal limbs of the preopercular ai^e about 

 equal in length, and enclose an angle of 100 degrees. The nasal 

 bone is small and tubulai- ; there is a postorbital bone of moderate 

 size, two suborbitals, two preoi'bitals, the upper one smaller than 

 the lower, and a narrow bone lying antero-dorsally to the orbit. 



The gape is so small that, although the premaxilla is small and 

 the maxilla large, the latter forms only a small portion of the 

 oral border when the mouth is opened to its widest extent. There 

 is but a single sur maxilla*, which from its shape and position is 

 clearly to be identified with the posterior of the two present in 

 Clupea. The angular bone is distinct. The mandibular ramus 

 stands high, and the highest point is situated far forwards ; the 

 outline of the ramus is intermediate between that of Clupea 

 harengus and that of Chatoessus (text-fig. 128, p. 466). There 

 are no teeth on the dentary, and none on the premaxilla, maxilla, 

 palatine, entopterygoid, ectopterygoid, and vomer. 



The opercular bones are normal ; there are five branchiostegal 

 rays on each side ; the interhyal is bony ; there are two hypohyals, 

 the lower larger than the upper. The glossohyal is long, narrow, 

 with minute teeth ; the urohyal is large and extends backward 

 considerably behind the posterior limit of the epihyal. 



Chatoessus erebi. 



Material examined. — In addition to a skull specially prepared 

 for the purposes of this investigation from an alcohol-preserved 

 specimen kindly furnished by Prof. G. B. Howes, two skulls were 

 examined, belonging to complete skeletons in the Osteological 

 Collection of the British Museum (67.5.6.99 and 67.5.6.5, both 

 from Cape York, N. Australia). 



Cranium (text-fig. 126, p. 464). — The cranium is stout and 

 rather broad, and is remarkable for the spines that project from 

 the squamosal, postfrontal, and prefrontal bones. The middle part 

 of the parasphenoid is greatly depressed, which gives an appearance 

 of considerable depth to the middle of the cranium. 



The parietals are separated by the supraoccipital. There is an 

 oval temporal foramen, situated near the anterior end of the 

 posterior temporal groove, bounded by the frontal and parietal, 

 and leading directly into the cranial cavity. Behind this, and at 

 a sUghtly lower level, is a deep pre-epiotic fossa, bounded above 

 by the parietal and epiotic, and below by the squamosal and epiotic. 

 It extends inward and upward as far as the supraoccipital. 



Thei-e is a subspherical cavity in the pro-otic, and another, 

 rather larger, in the squamosal, for the accommodation of vesicles 

 of the swim-bladder; but since these do not appear as bullate 

 projections on the surfaces of the bones, it is necessary to dissect 



* Smith Woodward (Brit. Mus. Cat. Foss. Fishes, iv. p. 139) records Biplomystus 

 as having two surmaxilla?. There is a possibility that one surmaxilia had been lost 

 from each side of the skull examined by me before it came into my hands, but from 

 the appearance of the maxillary series of bones I do not think that this is at all 

 likely. 



