!^6 PAPERS FROM TORTUGAS LABORATORY vol. xxxiv 



by each of the united elements may be made out by noting the relation the ridges 

 on its sides bear to the articular surfaces, and by examining interhemals next in 

 series. It becomes clear then that although one might say that in some of these 

 fishes the second interhemal is long and spear-shaped, it is never correct to state 

 that that bone is "expanded into a hollow cylinder into which the air bladder 

 enters." 



In Gcrres cinereus, for example, the morphological first interhemal is essen- 

 tially a flat plate, which is united along its posterior margin to the laterally ex- 

 panded, long, tapering second interhemal. Its free anterior border is more or 

 less thickened, without trace of excavation, and in cross section at mid-length is 

 simply rounded. 1 



Species here referred to Eucinostomus agree in having the anterior border of 

 the first interhemal broad and concave in cross section at mid-length. Besides 

 differing in details later mentioned, they are unlike in the extent to which, 

 toward the articular end, the borders of this hollow element grow toward one 

 another to enclose the tip of the air bladder. W. H. L. 



Eucinostomus Baird and Girard 



Eucinostomus Baird and Girard, Smithsonian Inst. 9th Rept., 1854, p. 344 (E. argenteus 



Baird and Girard). 

 Ulaema Jordan and Evermann, in Jordan, Proc. Calif. Acad. Sci., ser. 2, vol. 5, 1895, p. 471 



{Diapterus lefroyi Goode). 



An incorrect idea regarding the structure of the falsely called "second inter- 

 hemal" furnished Jordan and Evermann (see citation above), as Parr (Bull. 

 Bingham Oceanog. Coll., vol. 3, art. 4, 1930, pp. 61-66) observed, with a generic 

 difference in Eucinostomus lefroyi which is fancied only. At first glance the 

 simplest of these interhemal structures might seem to be that of E. havctna, for 

 in it the hollow bone, receiving the tip of the air bladder, is widest open an- 

 teriorly. But in its sculpturing toward the articular extremity it is more complex 

 than in E. lefroyi. It shows two pairs of ridges, an anterior and a lateral pair, 

 whereas the species last named has only one pair of ridges. This single pair con- 

 tinues dorsally close together but not in real union, and forms the conical re- 

 ceptacle, slit open on the anterior side, in which the tip of the air bladder rests. 



Though narrow, the anterior fissure is evident in the other species of 

 Eucinostomus here considered. In two of the three species available for dissec- 

 tion, however, greater complexity of structure is attained; in these both anterior 

 and lateral ridges appear to have grown forward to enclose the bladder tip, for 

 the investing bone has an outer and a delicate inner lamina on either side of the 

 median fissure. W. H. L. 



1 Gerres is characterized, furthermore, by the peculiar swim bladder, which is bifurcate 

 both anteriorly and posteriorly (Meek and Hildebrand, Field Mus. Nat. Hist., Zool. Ser., 

 vol. 15, 1925, pt. 2, p. 590; Parr, Bull. Bingham Oceanog. Coll., vol. 3, art. 4, 1930, p. 64). 

 In Eucinostomus, at least in calif orniensis, the air bladder tapers posteriorly and ends in a 

 sharp point. Anteriorly it has two small appendages (Meek and Hildebrand, op. cit., p. 585). 

 — S. F. H. 



