PISCES. 187 
Oaleus. Gill melids this name into EugaUus, Proc. Acad. Nat. Sc. 
Philad. 1864, p. 148. 
Mustelus. Mr. Gill describes two new species, viz. M. calif ornicus and M. \/ 
dorsalis, the latter from Panama, and proposes for M. Icevis the name of 
Eleuracromrjlon Icevis. Proc. Acad. Nat. Sc. Philad. 1864, p. 148. 
Triads. According to Mr. Gill, Mustelus felis (Ayres) should he refen-ed 
to this genus. Proc. Acad. Nat. Sc. Philad. 1864, p. 149. 
Polyprosopus (Couch). Mr. Gill expresses his conviction that this fish 
belongs to the genus Cetorhinus or Selache, and that the differences observed 
are probably due to distortion or defective observation. Proc. Acad. Nat. 
Sc. Philad. 1864, p. 207. 
Cestracion phillipii. A detailed description with figures of the Port Jack- 
son Shark has been given by Striiver,^ Nov. Act. Acad. Carol. Leop. Nat. 
Cur. xxiii. 1864. 
NotorTiynchus (Ayres). Mr. Gill makes some remarks on this genus, and 
distinguishes a Kotorhynchus borealis besides K. maculatus. Proc. Acad. Nat. 
Sc. Philad. 1864, p. 149. 
RAJIDiE. 
Rata baits. Prof. Wyman has made investigations into the 
development of this species, Mem. Amer. Acad. 1864, ix. p. 31. 
The more important conclusions arrived at are stated as follows 
at the close of the paper (reprinted in Ann. & Mag. Nat. Hist. 
1864, xiv. p. 399) 
(1.) The yelk-case is formed in the glandular portion of the oviduct, and 
is begun previously to the detachment from the ovary of the yelk which is 
to occupy it. 
(2.) Tlie embryo, before assuming its adult form, is at first eel-shaped and 
then shark -shaped. 
(3.) The embryo is for a short time connected with the yelk by means of 
a slender umbilical cord j the cord afterward shortens, and the young skate 
remains in contact with the yelk until the end of incubation. 
(4.) There are seven branchial fissures at first : the foremost of these is 
converted into the spiracle, which is the homologue of the Eustachian tube 
and the outer ear-canal ; the seventh is wholly closed up, and no trace re- 
mains ; the others remain permanently open. 
(5.) There are no temporary branchial fringes or filaments on the first and 
seventh arches j on the others the fringes are developed from the outer and 
convex portion of the arch, and are not at first prolongations of the internal 
gills. 
(6.) The nostrils, as in all Vertebrates, consist at first of pits or indenta- 
tions in the integuments ; secondly, a lobe is developed on the inner border 
of each ; and finally the two lobes become connected, and thus form the 
homologue of the fronto-nasal protuberance. The transitional stages corre- 
spond with the adult conditions of them in other species of Selachians. 
(7.) The nasal grooves are compared with the nasal passages of air- 
breathing animals, and the cartilages on either side of these to the maxillary 
and intermaxillary bones. 
(8.) The foremost part of the head is formed by the extension of the facial 
