464 Gobioidei, Discocephali, and Tzniosomi 
I thought I would try to find it also, and to this end sallied 
out one morning, armed with a spade, and commenced pros- 
pecting in a marsh at Berkeley, not far from the State Univer- 
sity. For a long time I was unsuccessful, as I did not know by 
what outward signs their habitations could be distinguished, 
and the extent of mud-bank left bare by the retreating tide 
was, as compared with my powers of delving, practically limit- 
less. 
“At last, toward evening, while digging in the bend of a 
small creek, in a stratum of soft, bluish mud, and at a depth of 
about a foot below a small puddle, I found five small fishes, 
which at first I believed to belong to an undescribed species, 
so little did they resemble the typical G. mirabilis, but which 
proved, upon a closer examination, to be the young of that 
species. There was the depressed, broad head, the funnel- 
shaped ventral ‘disk’ formed by the union of the two ventral 
fins, and the compressed tail of the long-jawed goby, but where 
were the long jaws? The jaws were, of course, in their usual 
place, but their prolongations had only just begun to grow along 
the sides of the head, and were not noticeable unless looked for. 
A comparison of the various specimens proved conclusively 
that the strange-looking appendage is developed during the 
growth of the fish, as will be seen by the following measure- 
ments of four individuals: 
“Tn the smallest specimen the maxillary expansion extends 
beyond the orbit for a distance about equal to that which inter- 
venes between the anterior margin of the orbit and the tip of 
the snout; in No. 2 it reaches to the posterior margin of the 
preoperculum; in No. 3 it ends level with the gill-opening; 
while in the largest individual it passes the origin of the pectoral 
and ventral fins. 
‘What can be the use of this long fold of skin and cartilage, 
which is not attached to the head except where it joins the 
mouth, and which, from its gradual development and ultimate 
large dimensions, must certainly serve some useful purpose? 
“Do not understand that I mean that every part of a crea- 
ture is of use to it in its present mode of life, for, as all natural- 
ists know, there are in structural anatomy, just as in social 
life, cases of survival; remains of organs which were at some 
