MUSEUM OF COMPARATIVE ZOOLOGY. 



167 



Peristedium platycephalum, n. sp. 

 The length of the type to tip of snout, without prolongations, is 145 mm. 



Body much depressed, its greatest height (23 mm.) 6^ in body length, 6| in 

 total. 



Length of head without prolongations (47 mm.), twice the height of body, 3^ 

 in its length, with prolongations i\ in body length. Interorbital space deeply 

 concave, the supraorbital margin being swollen, its width (14 mm.) equal to the 

 long diameter of the eye. No protuberance on the forehead, which is much 

 depressed, its outline descending abruptly and rapidly in front of the eyes. A 

 ridge below the eye, not armed; a small vertical spine behind each nostril. 

 Stout spines upon operculum and several upon the vertex. The length of the 

 snout with its extensions (29 mm.) is half the length of the head, its processes 

 (10 mm.) about 3 in its own length. The processes are flat, triangular, di- 

 verging slightly, the distance apart of their tips 2-2^ that at their bases. A 

 ridge extends backwards from the base of each process along the lower edge of 

 the preoperculum, ending behind in a sharp flat spine, the greatest width of the 

 expanded portion, on the preoperculum, only \ as wide as the eye. Beneath 

 this is another less conspicuous ridge with minutely serrated edge, which is 

 double in front and single behind, the two portions separated by a slight notch. 

 Jaws normal, the two tentacles much fringed, their length (16 mm.) not 

 much exceeding the diameter of the eye ; between them, and placed about equi- 

 distant from each other, are two bunches of short tentacles, about four in each. 

 Chin with numerous short tentacles, some of them as long as the eye, arranged 

 for the most part in bunches of four- 

 Maxilla does not reach to the anterior margin of orbit. 



Diameter of eye (13 mm.) nearly four in greatestlength of head, and exactly 

 half total length of snout. Greatest width of head, over the preopercular 

 ridges (43 mm.), nearly equal to its own length without the processes. Dorsal 

 origin over the upper angle of gill-opening. The fin has 8+17 rays. The 

 length of the longest spine (18 mm.) is equal to that of postorbital portion 

 of head. 



