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Show DR. W. G. RIDEWOOD ON THE CRANIAL [May 3, branchial is peculiar, the upright limb being exaggerated, and the forward one reduced to such an extent that not only does it fail to run along the mesial edge of the second pharyngobranchial, but it does not even touch it. Text-fig. 18. Albula eonorhyncJnis, hyobranchial skeleton, dorsal view. The epibranchials and pharyngobranchials of the right side are not shown. For explanation of lettering, see p. 81. B a th y th r is s a d orsalis (Pterothrissus gisu). I am pleased to be able to confirm a suggestion made by Boulenger (" Revision of the Mormyiidje," Proc. Zool. Soc. 1898, p. 776) that Bathythrissa is not intimately related with the Salmon idse, with which family Gunther had associated it (Ann. & Mag. Nat. Hist. (4) xx. p. 443; Chall. Rep. Deep-Sea Fishes, p. 221), nor with the Clupeidre, with which family Gill grouped it (Mem. Nat. Acad. Sci. Wash. vi. 1893, p. 131), but is nearly allied to Albula. Smith Woodward is evidently of the same opinion as Boulenger, for in placing the genus Istieus in the family Albulidse, he remarks that Bathythrissa is not clearly distinguished from Istieus (Brit. Mus. Cat. Foss. Fishes, iv. 1901, p. 67, also Introduction, p. vii). The posterior temporal fossae are completely roofed over, as in Albula, but the lateral temporal fossae are much shallower. The relations of the opisthotic, parietal, and supraoccipital are as in Albvla, except that the supraoccipital crest is smaller. The basi- |