1904.] OSTEOLOGY OF THE ELOPID.E AND ALBULIO.E. 53 



occipital and the lower parts of the pro-otics are inflated, just as 

 in Alhula, but the subtemporal fossae are larger and shallower. 



The parasphenoid and entopterygoid teeth are more pointed 

 than those of Albida; the vomer and palatine are edentulous. 

 The eye-muscle canal has no posterior opening ; the basisphenoid 

 is relatively smaller ; the interorbital septum, below the orbito- 

 sphenoid, is membranous ; the prefrontal is of slighter con- 

 struction ; the oval space in the front part of the parasphenoid is 

 very small ; the ethmoid i-egion of the cranium is a little shorter 

 in proportion ; the top of the mesethmoid has no groove, but the 

 oval foramen seen in a side view of the mesethmoid is present. 



The shapes, proportions, and relations of the supratemporal and 

 post-temporal ai-e the same as in Alhula, although I have not 

 recognised the ossified tendons of the post-temporal projecting 

 into the posterior temporal fossa. The sensory canals of the head, 

 judging by the shapes of the superficial bones, are even relatively 

 larger than in Albula. The circumorbital bones, the premaxilla, 

 maxilla, and surmaxiila do not differ mateiially from those of 

 Albula. Glinther (l. c.) says " maxillary with a marginal row of 

 very small teeth," but this I cannot confirm. 



The mandible difiei's in shape in consequence of the coi'onoid 

 process being situated farther forward ; it is in the posterior half 

 of the ram VIS in Albula, but in the anterior half in Bathythi^issa. 

 The sesamoid articular of Bathythrissa is unossified. The hyo- 

 palatine arch resembles that of Albida, except in the matter of 

 teeth, noted above ; the process of the ectopterygoid which passes 

 outward and backward in the floor of the orbit to join one of the 

 suborbital bones is longer aiad more slender ; the nodule of 

 cartilage which iw Albida is ossified to form the posterior endosteal 

 palatine is unossified in Bathythrissa, and is connected by a strong 

 ligament with a process of the orbitosphenoid which is directed for- 

 ward and downward, and lies on the mesial side of the prefrontal. 



The subopercular is smaller than in Albula, but is of the same 

 general shape ; the ventiul edge of the interopei-cular is notched 

 at a little behind the middle of its length. The sensory tube, 

 which runs in the lower edge of the preopercular and beneath the 

 ramus of the mandible, is evidently larger in Bathythrissa than in 

 Albula. There are only six branchiostegal rays, instead of fifteen 

 as in Albida. The first four arise from the outer surface of the 

 ceratohyal, the next from the junction of the ceratohyal and the 

 epihyal, and the last from the outer sui'face of the epihyal. 



The only differences to be noted in the hyobranchial skeleton 

 are that the glossohyal has its own teeth, confined to the posterior 

 fourth of its surface, and is not overlapped by the dentigerous 

 membrane-bone that belongs to the three basibranchial bones. 

 The basibranchial teeth stand higher, and are less hemispherical 

 than in Albida. 



Comments on the Skull of the Elopidse aoid Albulidfe. 



In reviewing the characters which are common to the skull of 

 the Elopidse "and the Albulida^, it is perhaps natural that we should 



