436 MR.J.¥. JOHNSON ON A NEW TRICHIUROID FisH. [May 9, 
teen. It may be further noticed that in the present fish the ventral 
spines are placed under the posterior angle of the base of the pec- 
toral fin, instead of being inserted a little before that fin, and that 
the lateral line does not descend rapidly under the anterior part of 
the first dorsal fin, as in Prometheus atlanticus. With Nesiarchus 
nasutus it cannot be confounded, since the latter has perfect ventral 
fins and fleshy and cartilaginous prolongations of the jaws. 
The dimensions of the fish which has afforded materials for this 
description are given in the following table :— 
inches 
Total ldnpthoffishisz imo cene LE E BO 10 
Heishti 1. ss ayeik of wis odie wee softtt ane iiie 
Thickness behind pectoral..... 0... ..0220----0 35 
Head) length ad: ep. tisk\ ts cel ee ie OR AE 20 
Eye, diameter, early. siee). D2. ances oe o/h. 3 
Teeth, lengthvof largest !..saj0. iss et esiehs ore nial intel + 
First dorsal, distance from muzzle .... J eee, 
First dorsaldempthi 32 ....areu Aol Cad ARLES nt 41 
First dorsal, height in front ..... mig tSeR. ae 5 
Second dorsal, length ............ 135 
Second’ dorsal,j height bis esis. ile ee Nyse See 
Pectoral, distance from tip of lower jaw..........- 2545 
Péetoralydengtly i s4dn maby it ouk tehad soe seget. 1,3; 
Ventral spines, length linccle Jatin a. fiat Bae i 
Ventral spines, distance from tip of lower jaw .. 2545 
Spine in front of anal, length ................-. sy 
Anal; denetiietos Ja) wtetis ota ace Dore chin aes» 1,5 
Agal, height infront: als ool. nels bie conse" eae oper Ta 
Caudal Agmethi ec 7 Se sA Ip sciW olitote cA I. el AR BOE 13 
The family of Trichiuride is composed, according to Dr. Giinther’s 
Catalogue, of the genera dphanopus, Lepidopus, Trichiurus, Epin- 
nula, Dicrotus, Thyrsites, and Gempylus. To these have to be added 
the recently described genera Nesiarchus and Nealotus. With re- 
spect to Dicrotus, Giinther, a genus founded on a small fish only 
24 inches in length, it appears to me that it ought to be abolished, 
the fish having been most probably a young individual of some species 
of Thyrsites or Gempylus—an opinion which has been entertained by 
Dr. Giinther himself for some time. From Thyrsites prometheus, 
for example, it would seem to differ only by the absence of finlets 
and the presence of minute teeth on the vomer. But finlets are not 
developed in very young fishes, such as Dicrotus armatus probably 
was; and teeth are apt to disappear from the vomer when fishes ac- 
quire their full growth. It may be mentioned in confirmation of 
this view, that I obtained a scaleless fish, not quite six inches in length, 
which had its ventrals reduced to single spines, had teeth on both 
palatines and the vomer, and had the last four or five rays of the 
second dorsal fin distant from, and unconnected by membrane with, 
the rest of the fin; whilst the last two or three rays of the anal fin 
were separated from the anterior portion. This was therefore a Di- 
