Leptocephalus acuticeps — Orton 
199 
Stromman and L. lanceolatoides Schmidt, en- 
compass larval populations that represent sev- 
eral species of Serrwomer . The available data 
suggest that L. acuticeps is probably also an 
indicator of group relationships. The many basic 
morphological and color-pattern characters that 
acuticeps and larval Nemichtbys share have been 
sufficiently stable to withstand the amount of 
evolutionary divergence that now separates the 
genera Avocettina and Nemichtbys . Hence the 
existing intrageneric variation in these characters 
undoubtedly has even narrower limits. Since all 
species in the Avocettina group (including La- 
bicbthys and, tentatively, Avocettinops ) thus 
probably have very similar larvae, I have elected 
to treat L, acuticeps in a practical sense as a 
larval group category that designates, compre- 
hensively, the general kind of larva that is 
characteristic of the avocettinas as a whole. This 
avoids the needless redundancy of establishing 
a new formal (but temporary) leptocephalus 
name for each ostensibly different minor popu- 
lation within the Avocettina group. 
A more detailed understanding of larval dif- 
ferentiation within this group of eels awaits not 
only the study of more extensive larval collec- 
tions but also additional taxonomic work on 
the adults. The number of valid species and 
genera of avocettinas is uncertain, and a world- 
wide revision of the group is needed. Problems 
that await study include the status of the genus 
Avocettinops. Is its single recognized species, 
Avocettinops schmidti Roule and Bertin, a dis- 
tinct entity, or is it based on spawned-out, 
senile individuals of Avocettina spp. with re- 
gressive skeletal characters? 
Much remains to be learned about the color- 
pattern characters of nemichthyid larvae, par- 
ticularly with respect to developmental changes 
and population differences. The known larvae of 
the avocettinas ( Leptocephalus acuticeps ) are 
more heavily pigmented than are larvae of 
Nemichtbys , both in the density of the markings 
that they share and in the presence of additional 
pattern elements. Since the evidence of evolu- 
tionary trends in color patterns commonly con- 
sists of simple modifications of a recurring basic 
pattern, the characters of these known nemich- 
thyid larvae suggest some pattern variants that 
might reasonably be watched for among other 
closely related but still undiscovered larval pop- 
ulations. In such larvae, certain parts of the 
pattern might be less fully developed than they 
are in known larvae of Nemichtbys , or the pat- 
tern might be still more complex than it is in 
the known specimens of L, acuticeps. The char- 
acteristic internal-spot pattern might be modi- 
fied, or it might be totally absent, as . has been 
reported for type "B” larvae of Nemichtbys 
(Roule and Bertin, op. cit.). The scattered, in- 
conspicuous internal melanophores that supple- 
ment these spots in the Scripps larvae of L. 
acuticeps might be more heavily developed in. 
some related larval populations. 
The assignment of Leptocephalus acuticeps 
to the Avocettina group provides information, 
that is useful for various evolutionary studies. 
Since L. acuticeps has a more generalized format 
than do the extremely attenuated larvae of 
Nemichtbys , L. acuticeps probably more nearly 
represents the basic nemichthyid larva and it is, 
consequently, the more important larva to treat 
in comparative studies on the evolutionary af- 
finities of the nemichthyids to other eels. The 
ostensible morphological similarity between 
nemichthyid and congrid larvae is one of the 
problems that needs inquiry. Both L. acuticeps 
and the larva of Nemichtbys show sufficient 
resemblance to congrid larvae, especially in the 
various proportional characters thar^are associ- 
ated with the gut length, to suggest the need 
for a renewed study of the relationships of these 
two families, which are usually placed far apart 
in the classification. Although the available 
evidence does not warrant any assumption that 
these two families are more closely related than 
hitherto suspected, it does suggest that future 
work on leptocephali may profitably emphasize 
a more intensive comparative study of their basic 
anatomy so that the phyletic significance of their 
obviously diversified characters can be evaluated 
and used more effectively in eel systematics. 
SUMMARY AND CONCLUSIONS 
Regan (1916) based the South Atlantic eel 
larva, Leptocephalus acuticeps , on a single 47- 
mm specimen, which Bertin (1936) later re- 
examined and discussed in greater detail. The 
relatively complete published data and the un- 
usual nature of certain of the characters set 
