ON THE DISTRIBUTION OF THE GENERA. 367 
gas, Lemonema, Phyciculus, Bregmaceros, Trachyrhynchus, Monolene, 
Symphurus, Argyropelecus, Bathypterois, Maurolicus, Chauliodus, Idiacan- 
thus, Alepocephalus, Halosaurus, Uroconger, Congermurena, Ophichthys, 
Cryptopterus, Venefica, Serrivomer, Labichthys, 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 migration. 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: Raia, 
Hoplostethus, Trachichthys, Melamphaés, Trichiurus, Chiasmodus, Lophius, 
Chaunax, Dibranchus, Peristedium, Callionymus, Dicrolene, Monomitopus, 
Diplacanthopoma, Macrurus, Symphurus, Sternoptyx, Argyropelecus, Chlor- 
ophthalmus, Bathypterois, 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 Jack 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 summa- 
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 the 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 
