78 DR. W. G. RIDEWOOD ON THE CRANIAL [May 3, 



RocGus (Proc. Wash. Acad. Sci. iii. 1901, pi. Ixiv.), allude to the 

 hypohyal as the basihyal. Owen (Anat. of Vert. i. 1866, pp. 106 

 & 124), it is true, used the word basihyal in this sense, and was 

 followed by Gunther (' Study of Fishes,' 1880, p. 58) and others ; 

 but the homology between the glossohyal of the Teleostean and 

 the basihyal of the Elasmobranch is now so firmly established that 

 there is no justification for reviving an erroneous terminology. 

 What is more incomprehensible than the retention of an obsolete 

 application of the tei-m basihyal is the fact that Starks, while 

 calling the hypohyals the basihyals in 1901 {I. c), designates them 

 hypohyals in 1898 and 1904 (Proc. Calif. Acad. Sci. (3) i. 2, 1898, 

 pi. xxiii. fig. 8, Sehastolohus ; and Proc. U.S. Nat. Mus. xxvii. 

 1904, p. 603, Berycoid fishes). 



Most writers are in agreement as to the application of the 

 terms epihyal and ceratohyal, but Allis has adopted an unusual 

 nomenclature which appears to have very little to recommend it 

 beyond the fact that it serves to locate the main jointing of the 

 hyold arch between the epi- and cerato-elements, as occurs in the 

 branchial arches ; he regards the epihyal as a part of the cerato- 

 hyal (which is, according to his view, a double ossification), and 

 calls the interhyal the epihyal (Journ. Morph. xii. 3, 1897). 



The glossohyal or basihyal varies greatly in size, being largest 

 in Hyodon, and extremely reduced in J^ngrmdis and Coilia. 

 There is no separate glossohyal in the Mormyridse ; it is either 

 wanting, or is fused with the first basibranchial. An endosteal 

 glossohyal is frequently present in addition to the ectosteal and 

 usually dentigerotis bone (e. g., Alhula, Ghirocentrus, Megalops), 

 but in such forms as Heterotis, Osteoglossum, Chatoessus, Clupea, 

 and Alepocephahhs the cartilage remains unossified. 



The dentigerous plate which covers the first, second, and third 

 basibranchials is readily removable in Arapaima, but in most 

 cases it is fused with the second, and overlaps the hinder part of 

 the first basibranchial and the anteiior part of the third basi- 

 branchial (e. g., Chopea, Ckirocentrus, Engraulis). In Hyoclon it 

 is fused with the third as well as with the second basibranchial, 

 and in JJbiola it is fused with all three basibranchials, and over- 

 laps, but is not fused with, the posterior half of the glossohyal. 

 It is much reduced in size in Chatoessus, in which it is edentulous ; 

 and in Gonorhynchus it is confined to the second basibranchial. 

 In Duss'umieria each of the three basibranchials has its own 

 dentigerous investing bone. There is in most cases also a much 

 smaller dentigeious bone covering the plate of cartilage that 

 represents the fourth and fifth basibranchials. 



The first basibi'anchial is unossified in Heterotis, N'otopterus, and 

 Gonorhynchus. The second basibranchial is remarkably long in 

 Engraulis, and the parallelism of the first and second cerato- 

 branchials is much disturbed in consequence. In Chanos the 

 anterior ends of the fourth and fifth ceratobranchials are separated 

 by a narrow, elongated tract of cartilage; in Alejjocej^halus a,iid 

 Chatoessus the anterior ends of the third and fourth cerato- 



