DISCUSSION OF SPECIES AXD THEIR DISTRIBUTION. 473 



sion, is equal to the leugtli of the head; the preoiliital extension about two-fifths of the 

 length of the snout. The prcoibitnl jiiocesses are Hat, uuaiincd, and somewhat divergent; 

 a ridge arises at the base of the pi-eorbital jirocess and extends to the angle of the preoper- 

 culuin, where it terminates in a blunt spine; a low ritlge on the operculum, ending in a 

 rather inconspicnons spine; another above, and close to it, i)ointing upward. The length 

 of the oj)crcular ridge of spines is nearly equal to the horizontal diameter of tlie eye. 



Jaws feeble and apparently toothless; barbels on the lower jaw so inconspicuous at 

 present as to be scarcely visible. 



The maxillary extends almost to the vertical through the anterior margin of the eye; 

 the diameter of the eye is contained 4 times in tiie length of the head without its pro- 

 longations. 



The dorsal origin is over the tip of the opercular spine ; the origin of the anal apparently 

 behind that of the second dorsal; ventrals slightly in advance of the pectorals, and not so 

 far back, tliough their tips reach somewhat beyond the vent; pectorals rather long; about 

 twenty-five rows of scales. 



Tlie type, about 2 inches in length, is in the Museum of Comparative Zoology at 

 Cambridge, and has been studied in the preparation of this description, but the example 

 being unique and very small, we have not ventured to examine it so closely as would have 

 been practicable with more mateiial. It is, however, ai)parently a well marked specie.s, 

 resembling in a general way 1\ lonyispatha. It was obtained by Poey from the stomach 

 of Poli/mixia nobilis, taken near Cuba in deep water. 



PERISTEDION GKACILE, Goode ami Bean, ii. s. (Figure 387). 



Body very slender; its greatest height (18 millimeters) is nearly one-sixth of its length. 

 The length of the head to the tip of the prolongated rostral spine is 48 millimeters ; without 

 the jtrolongatioiis its length is ."^C millimeters or twice the greatest height of the body. The 

 interorbital space is deejjly concave. The interorbital width (10 millimeters) equals one-half 

 the length of the snout including the rostral spine. The forehead descends gently towards 

 the snout and the supraorbital crests are very little elevated. The rostral spine on each 

 side is continued backwai'd by a slight bony ridge ending in a blunt spine at the angle of 

 the preopercuhim. Thc^ opercular spine is small, the length of the oiieiculum with the 

 spine being about equal to the length of the eye. The length of the snout with preorbital 

 extension (29 millimeters) is a little more than one-fourth of the standard length ; the length 

 of the spine alone (1.3 millimeters) is nearly equal to the length of the mandible. The jaws 

 are feeble and toothless. The length of the maxilla (12 millimeters) is one fourth the length 

 of the head. The length of tln^ mandible (15 millimeters) is one half the length of the 

 snout with the pn^orbital extension. Tlic^ mandible has two groups of barbels, one on each 

 side of its lower edge. The length of the longest barbel (!) millimeters) equals that of tlie 

 eye. The barbels are subdivided into several fringes; the number of barbels on each side 

 of the mandible may be divided up into 8 or 9 clusters. The mandible extends to the ver- 

 tical through the front of the eye. Twenty six gill-rakers on thi^ first aicli, the longest one- 

 half as long as the eye. The longitudinal diameter of the eye (9 millinu'ters) is nearly 

 equal to the width of the interorbital space. Greatest width of the head over the preorbi 

 tal ridge (15 millimeters) is one-half the length of the snout iiudiuling the ])reorbital exten 

 sion. The spinous dorsal originates directly above the end of the opercular tlap; the first 

 si)ine is slightly the longest, its length (15 millimeters) equals the length of the snout and 

 its projecting spine; it also ('([uals the short diameter of the eye. The longest ray of the 

 second dorsal (II millimeteis) is nearly one fourth the length of the head. The least height 

 of the tail (■'> millimeters) is one-third the length of the eye. The anal origin is under the 

 second ray of the soft dorsal; the fin extends as far back as the dorsal, the length of its 

 base (41 7iiillimeters) being 4 times the width of the interorbital area, the rays 

 about as long as those of the second dorsal. The length of the middle caudal rays (12 

 niillinjeters) is four-thirds the length of the eye, the tin being emargiuate. The ventral 

 base is under the pecti)ral base, the fin reaching to tlie vent, its length (18 millimeters) twice 



