ON THE DISTRIBUTION OF THE GENERA. 367 



gas, Lasmonema, Pliyciculus, Bregraaceros, Tracliyrhynchus, Monoleiie, 

 Symphurus, Argyropelocus, Bathyptero'is, Manrolicus, Chauliodus, Idiacan- 

 thus, Alepocephalus, Halosaurus, Uroconger, Congermuraina, Ophiclithys, 

 Cryptopterus, Venefica, Serrivomer, Lablchtliys, Nemichthys. This large 

 proportion of all the genera secured might be regarded as much more con- 

 clusively proving the existence of a Central American connection between 

 the Atlantic and the Pacific if it were not that the determined ranges are 

 only partial and that, presumptively, by future collecting they will in many 

 cases if not in all be extended into the polar waters. 



In regard to a former strait through the isthmus of Suez the testimony 

 of these genera is even more unsatisfactory than that concerning one 

 through the isthmus of Panama, as Africa does not extend so far south as 

 South America does by more than eighteen degrees and consequently is 

 much less of a barrier to nn'gration. The known ranges of the following 

 may be cited as less or more remotely favoring the theory of a recent 

 connection between the Mediterranean Sea and the Indian Ocean : Eaia, 

 Hoplostethus, Trachichthys, Melamphaes, Trichiurus, Chiasmodus, Lophius, 

 Chaunax, Dibranchus, Peristedium, Callionymus, Dicrolene, Monomitopus, 

 Diplacanthopoma, Macrurus, Symphurus, Sternoptyx, Argyropelecus, Chlor- 

 ophthalmus, Bathyptero'is, Chauliodus, Bathytroctes, Alepocephalus, and 

 Uroconger. 



Lamprogrammus, Scopelengys, Narcetes, and Xenomystax have been 

 discovered in the Panamic area and in the northern portions of the Indian 

 Ocean only, and Acanthonus has been secured north of New Guinea, in 

 the Philippines, and in the Panamic section of the Pacific. The immense 

 gaps apparently existing in these distributions are more likely to be due 

 to lack of search than to actual absence from the immense spaces inter- 

 vening between the points at which species of these genera have already 

 been obtained. 



A better idea of the general distribution, and of the weight and present 

 condition of the evidence relating to former straits near Panama and in the 

 neighborhood of Suez will perhaps be obtained from the following sunnna- 

 ries relating to such genera in the collection as have also been obtained in 

 other localities. 



Raja : — Occurring in the Panamic region of the Pacific, in tlie Caribbean, 

 the Mediterranean, the Arabian Gulf, the Bay of Bengal, the Indian Ocean, 

 on both sides of the Atlantic and of the Pacific, from north latitude of 80° to 



