DISCUSSION OF SPECIES AND THEIR DISTRIBUTION. 333 



PYCNOCRASPEDUM, Alcock. 



Tycnocraspedum, Axcock, Ann. and Mag. Nat. Hist., Nov., 1889, 386. 



Head large, body compressed, both covered entirely with small, thin, smooth, rather 

 deciduous scales. Head-bones and opercles spineless. Snout short, broad, and not over- 

 hanging the jaws, which are equal in front. Eye of moderate size. Moutb very large; teeth 

 in villiform bands in the jaws, palatines, and vomer. No barbel. Gill-openings wide, gill- 

 membranes entirely separate; 4 gills; 8 branchiostegals; no pseudobranchiic. Lateral line 

 incomplete on the tail. Vertical tins invested with thick, scaly skin. Caudal free, united with 

 the vertical tins at its extreme base only. Pectoral fins entire. Ventral fins in the form of 

 bitid lilameuts. 



The type and only species is P. squamipinne, Alcock (loc. cif.), taken in 193 fathoms in the 

 Bay of Bengal, in lat. 20° 17' 30" N., Ion. 88° 50' E. 



NEMATONUS, Gunther. 



Nematonus, Gunther, Challenger Report, xxir, 1887, 114 (tj-pe, Bathijonus pcctoralxs, Gonde and Bean). 



Body compressed, with long, tapering tail. Bones of head soft, muciferous channels 

 moderately developed, and with integument very thin or absent on the upper portion and 

 snout. Operculum cartilaginous and flat; a broad process near its upper angle correspond- 

 ing to the opercular spine in some of the related genera; the head otherwise unarmed, 

 though irregular by reason of the bareness of the cranial bones. Snout much depressed, 

 broad, rounded. .Taws equal in front; mouth very wide ; bands of villiform teeth in jaws, 

 on vomer and palatines. Barbel none. Eyes small. Vertical fins confluent; ventrals a 

 pair of bitid filaments close together, on the isthmus, close to the humeral symphysis. Gills 

 four, with very short lamina' and rather short, incurved, acicular gill-rakers on the first 

 arch, and nuich shortei', less numerous, spatulate ones upon tlie three other arches. Pseu- 

 dobranchiai rudimentary. No traces of a lateral line, though the bodyis covered with scales 

 of considerable size, almost as large as the eye, and the cheek with others still larger. 



Nematonus dift'ers from Ponxjadus not only in the absence of spines ui)on the head, as 

 Giinther has indicated, but in themucli less ossified opercular apparatus, in the shorter and 

 thicker head, in the absence of the three series of pores simulating lateral lines, and in the 

 tendency to prolongation in the lower rays of the pectoral, which increase from the upjier- 

 most to the lowermost in Nematonus, while Porogadus has a lanceolate fin, and also in the 

 extreme exsertiou of its caudal rays. 



NEMATONUS PECTOEALIS, (Goode and Bean), Gunther. (Figure 295.) 



liathi/onus pectoralis, GooDE and Bean, Proc. U. S. Nat. Mus., 1885, viii, 604. 

 Nematonus pectoralis, Guntheu, Challengor Report, xxir, 1887, 114. 



Body moderately elongate, much compressed, the tail much shorter and more robust 

 than in Basso.zetus catena. Its height (20 millimeters) equals 1| times the length of the 

 head and one-seventh that of the body. 



Head stoutish, not much compres.sed, lower than body, its length (31 millimeters) con- 

 tained 5i times in the body length. Snout compressed, broad at its tip, its length (0 milli- 

 meters) exceeding the diameter of the circular eye (.5 millimeters). Interorbital area 

 slightly convex, its width (11 millimeters) slightly exceeding twice the diameter of the eye, 

 3 times in length of head. 



Maxilla extending iar behind the eye, its length (19 millimeters) less than that of prc- 

 orbital portion of head. Mandible as long as postorbital portion of head (22 millimeters). 

 Jaws, vomer, and palatines, with narrow bands of villiform teeth, normally arranged. 

 Branchiostegals 8. Gill-lamella- very short. Gill rakers long and numerous, 18 on first 

 arch below the angle, 5 above, 1 of which are rudimentary. Pscudobranchi* present, but 

 very rudimentary. 



Anterior nostrils on the top of the snout and near the median line of the head, near 

 its tip, separated by a s^iace about equal to the diameter of the eye. Posterior nostrils in 

 ftout of the eye. 



