96 
few lamellae (ca. 20). This distinction is no 
doubt correlated with a change in food habits 
(Klausewitz and Eibl-Eibesfeldt, 1959). Also 
the habit of living colonially in sand tubes is 
unknown in other congrids. 
These differences and similarities seem to 
bear out Bdhlke’s (1957) contention that the 
Heterocongrinae should be regarded as a well- 
defined subfamily within the Congridae, That 
there are profound differences in behavior and 
ecology is undoubted, but these have not in- 
volved any fundamental changes in the basic 
congrid body plan. 
Until recently, little information has been 
available on the osteology of the family Con- 
gridae. However, Asano (1962) has presented 
detailed information on the anatomy of 10 
genera and 14 species of Japanese congrids. 
On the basis of his study, Asano recognized 
two subfamilies, the Anagoinae and the Con- 
grinae (the Heterocongrinae were not consid- 
ered). The Anagoinae were said to differ from 
the Congrinae in that there is a forward and 
laterally directed process on the ethmoid, the 
supraoccipital is absent, there are only four 
suborbitals, the abdominal and caudal vertebrae 
are about equal in number, the gas bladder is 
attached to the parapophyses, the tail-tip is hard, 
the caudal rays are short, the fin rays are un- 
segmented, and the lateral-line scales are well 
developed. 
Asano assigned two genera, Anago and Allo- 
conger , to the Anagoinae. I can confirm that 
Arias oma belongs here, as does the recently 
described Paraconger Kanazawa 1961. 
The heterocongrines share characters with 
both the Anagoinae and the Congrinae. They 
agree with the congrines in that the supraoc- 
cipital is present, there are many more caudal 
than abdominal vertebrae, and the gas bladder 
is free from the parapophyses. They agree with 
the anagoines in that the fin rays are unseg- 
mented, the caudal is reduced, and the lateral- 
line scales are well ossified (corresponding to 
Asano’s " Anago type”). I have been unable to 
determine with certainty the number of sub- 
orbitals in the heterocongrines. 
Gorgasia alone agrees with the Anagoinae 
in having a lateral ethmoid process. In this 
connection it is important to establish the evo- 
lutionary position of Gorgasia. Bohlke (1957) 
PACIFIC SCIENCE, Vol. XXI, January 1967 
gave reasons for considering Gorgasia to be in 
most respects the most primitive of the Hetero- ! 
congrinae. His conclusions are borne out in this 
study, except for the discovery in Gorgasia of ! 
peculiar, expanded transverse processes on the 
anterior vertebrae, and the loss of an anterior 
maxillary pedicel. These specializations proba- 
bly preclude Gorgasia as an ancestor, but they 
do not militate against the hypothesis that j 
Gorgasia is more generalized over-all, and prob- \ 
ably was an earlier offshoot of the heterocon- [ 
grine line. 
The retention in Gorgasia of a lateral ethmoid 
process indicates relationship with the anagoine 
line. It seems unlikely that the agreement rep- 
resents convergence. Eels have evolved a num- : : 
ber of structures bracing the maxillary, cor- j 
related with elongation of the gape and with the 
use of the jaws in biting and crashing (Gos- I 
line, 1951; Asano, 1962 ). However, the trend 1 
in heterocongrine evolution has been in the i! 
other direction, toward shortening of the gape ft 
and development of a jaw structure and denti- 
tion suitable for snapping at planktonic prey. 
It may be that the retention of the lateral eth- 
moid process in Gorgasia has allowed the loss i; 
of the maxillary pedicel. 
It seems plausible to hypothesize that the 
Heterocongrinae and Anagoinae arose from a 
common ancestor which had a lateral ethmoid 1 
process, a supraoccipital, unsegmented fin rays, ;j 
and well- developed lateral-line scales. It seems i ! 
likely that the sand-burrowing habit (known 
for Anago') had already been developed. The 
two groups have diverged sharply, however. 
The development of the plankton-feeding habit 
in the' heterocongrines has been accompanied 
by important changes in the head. The mouth 
has become short and oblique, and the denti- j 
tion specialized. The development of a short 
oblique mouth as an adaptation to snapping at 1 
plankton or small prey has taken place in a 
number of fishes. Compare, for example, the 
serranid genus Epinephelus , which feeds on 
relatively large prey, with the plankton-feeding 
Paranthias. A similar phenomenon can be seen 
if the bottom-feeding embiotocid genus Micro- |j 
metrus is compared with the closely related 
genus Brachyistius , which feeds in midwater !i 
(Hubbs and Hubbs, 1954). Walter A. Starck II 
has pointed out to me that the shortening of the J 
