Identification of Leptocephalus acuticeps Regan as 
the Larva of the Eel Genus Avocettina 1 
Grace L. Orton 2 
Regan (1916:140, pi. 7, fig. 5) based the de- 
scription of a distinctive new eel larva, Lepto- 
cephalus acuticeps , on a single 47 -mm specimen 
from the South Atlantic. He did not attempt to 
allocate this larva within the eel classification, 
but D’Ancona (1928:109) and Benin (1936:7) 
assigned it to the Congridae. Although no addi- 
tional specimens of L. acuticeps appear to have 
been reported since the brief original descrip- 
tion, Bertin re-examined the original larva and 
gave important supplementary information on 
it, and an additional illustration. 
Recent accessions of eel larvae from the 
eastern tropical Pacific in the Scripps Institution 
of Oceanography fish collection include two 
specimens that closely match the major known 
characters of Leptocephalus acuticeps. The pres- 
ent paper describes these larvae and assigns 
them to L. acuticeps . Comparative study indi- 
cates that L. acuticeps belongs to the Avocettina 
section of the family Nemichthyidae, and sug- 
gests that it is best interpreted as the general 
kind of larva that characterizes all of the avo- 
cettinas as a group. 
DESCRIPTION OF NEW SPECIMENS 
Collection data. The two larvae of Lepto- 
cephalus acuticeps from localities in the eastern 
tropical Pacific have the following collection 
data: 
(1) SI062-639-26A; from "Scot” expedition, 
Scripps Tuna Oceanography Program, Station 
No. 36; 6° 30' N, 95° 54.8' W; May 9 , 1958; 
total length 124 mm. (2) SI062-387-26A; 
1 Contributions from Scripps Institution of Ocean- 
ography, New Series. Manuscript received January 3, 
1963. 
2 Scripps Institution of Oceanography (University 
of California, San Diego), La Jolla, California. 
same expedition, Station No. 59; 5° 34' N, 81° 
28.5' W; May 18, 1958; total length 107 mm. 
Morphology. These are moderately slender 
larvae, with a long, straight gut, and a short tail 
( Fig. 1 ) . The smaller specimen has a total 
length of 107 mm; snout to anus, 97 mm; tail, 
10 mm. The larger has a total length of 124 
mm; snout to anus, 111 mm; tail, 13 mm. The 
maximum height is about 8% of the total length 
on the 107 -mm larva, about 1% on the 124- 
mm larva. The head proportions are quite gen- 
eralized, neither markedly elongated nor un- 
usually shortened, compared with other lepto- 
cephali in general (Fig. 2). The rounded eyes 
lack the thick white supporting pad ( "irido- 
choroid process”) that sheaths the eyeball of 
certain other leptocephali (notably, most con- 
grids ) . The snout profile is moderately concave. 
The jaws are moderately long and their tips are 
approximately even. The larval dentition, pre- 
senting no unusual features, consists of 12 or 
13 lanciform teeth on each side of the upper 
jaw, and 11 or 12 on each side of the lower 
jaw. The rather small first upper tooth on each 
side is attached to one of the pair of sliver-like 
rudimentary premaxillary bones that are close 
together on the upper tip of the ethmoid carti- 
lage. The other upper teeth border the maxillary 
and comprise 6 or 7 large ones followed by 5 
or 6 distinctly smaller ones. These size classes 
are more sharply defined in the 107-mm larva. 
The teeth on the lower jaw decrease in size more 
evenly. The small, subtriangular nasal capsule 
lies directly adjacent to the upper anterior 
quarter of the eye margin. The rounded an- 
terior nostril is smaller than the vertically ovoid 
posterior one; both are well defined, though 
small. The moderately large tongue rises well 
upward from the floor of the mouth, but neither 
its tip nor its sides project freely. The mod- 
erately large gill arches bear well-defined margi- 
186 
