Leptocephalus acuticeps — Orton 
191 
somites between the pylorus and the posterior 
end of the kidney. There is close agreement in 
the number of somites between the posterior 
end of the kidney and the anus. The differences 
in visceral proportions are consistent with the 
lower total somite count and the consequently 
shorter gut in the Scripps specimens. 
The pigmentation of the eastern Pacific larvae 
closely matches the known pattern of the At- 
lantic specimen. The internal supraspinal row 
of melanophores has essentially the same extent; 
the internal supra-intestinal row apparently ex- 
tends farther forward (Regan did not show any 
prepyloric pigment in this row); and the ex- 
ternal midventral row is apparently more com- 
plete (Regan showed no postpyloric pigment 
here). The original references did not indicate 
any middorsal pigment on the Atlantic larva. In 
the Scripps larvae the three internal spots are 
placed somewhat farther forward in relation to 
somite numbers, but (as will be discussed in a 
later section) they have essentially the same 
position in relation to the viscera and to certain 
blood vessels. Regan did not mention these spots 
in the original description, but Bertin discovered 
them, described them in detail, and figured one 
of them. These markings comprise an unusual 
pattern element which, so far as I can deter- 
mine, is known elsewhere only in the larvae of 
Nemichthys (see discussion below). The de- 
scriptions did not mention scattered internal 
melanophores anterior to the anus in addition 
to the three aggregate spots, but they did in- 
dicate that the tail bore small melanophores both 
above and below the median axis, and in Regan’s 
illustration this speckling forms essentially the 
same pattern as it does on the Scripps specimens. 
Although the maximum sizes that the Atlan- 
tic and Pacific larvae attain are still unknown, 
simple individual or growth-stage variation 
could account for most of the evident differences 
between the available Pacific larvae and the de- 
scribed Atlantic specimen. The smaller number 
of teeth, more concave head profile, slightly pro- 
truding lower jaw, slightly deeper body, and 
poorly defined hypurals of the original speci- 
men of acuticeps are developmental features 
that are commonly seen in young stages of lepto- 
cephali. Whether the minor color pattern dif- 
ferences represent growth-stage characters will 
remain uncertain until more complete develop- 
mental series are available. The difference in 
somite counts is the principal feature which sug- 
gests that the populations in the two regions may 
differ at the species level, but more data are 
needed before this difference can be evaluated. 
It is now pertinent to discuss the place of 
L. acuticeps in the eel classification. Apparently 
only two authors have compared acuticeps with 
other larvae (L. oxycephalus Pappenheim and 
L. magnaghii D’Ancona) , and only two have 
attempted to assign it to a category in the eel 
classification ( both to the same family, the Con- 
gridae ) . Elsewhere, however, one can find clues 
that clearly point to the proper taxonomic posi- 
tion of acuticeps . 
B. Leptocephalus oxycephalus 
Pappenheim (1914:190, pi. 9, figs. 3, 5) 
based his brief description of L. oxycephalus on 
seven Atlantic larvae that measured 177-193 
mm in total length, and he placed about 40 addi- 
tional smaller and less well-preserved specimens 
from the Atlantic and Indian oceans in oxyce- 
phalus with less certainty. He credited this larval 
form with total somite counts of 220-230, of 
which 180-190 were preanal. At about the 30th 
somite, he noted a structure that he tentatively 
identified as the liver anlage. He listed only two 
other characters, both rather uninformative: the 
head was low and the caudal fin was normal. 
Pappenheim did not mention pigmentation, and 
none is definitely apparent in his photographs 
of L. oxycephalus, but this does not necessarily 
mean that pigment cells actually were totally 
absent. It is quite possible that pigment had 
faded before he received the collection, or that 
the individual melanophores were too small to 
show on the photographs. In his descriptions of 
other leptocephali in the same paper, he tended 
to omit pigment characters or to treat them very 
superficially. Hence he may have considered the 
color pattern too insignificant to require detailed 
description. In Pappenheim’s illustrations the 
general format of L. oxycephalus rather closely 
resembles that of the Scripps specimens of L. 
acuticeps, but it also looks much like a very 
generalized congrid larva, and the characters 
discernible in the photographs are insufficient to 
permit definite discrimination. Regan (1916) 
considered his new L. acuticeps to be very simi- 
