376 G. B. GRASSI. 
phali. In’ correspondence with the small size of Lepto- 
cephalus brevirostris the number of larval teeth is 
small. Researches founded, firstly, on the enumeration of 
the myomeres; secondly, upon the enumeration of the dorsal 
and ventral arches of the vertebrae of the caudal extremity 
(hypurals) ; and thirdly, upon the enumeration of the posterior 
spinal ganglia, lead with great certainty to the conclusion that 
the Leptocephalus brevirostris is the larva of a Murenoid, 
the number of whose vertebree must lie between 112 and 117, 
most probably 114 or 115. Such a Murenoid is the Anguilla 
vulgaris. The Murenoid indicated cannot be any other of 
those occurring in the Mediterranean, because they all have a 
number of vertebre higher than 124.! Counting the myomeres 
in Leptocephalus brevirostris, one finds generally only 105 
complete, five others incomplete, and all the others in a state 
of transparency and incomplete formation. These latter are 
fortunately at the posterior extremity, where other criteria 
come to our assistance, namely, the spinal ganglia and the 
vertebral arches. To show how I arrive at the number of 
vertebree which must be possessed by the adult Individual, 
corresponding to a given Leptocephalus brevirostris, I 
quote the following example :—I assume that three vertebree 
develop themselves in correspondence to the first four incom- 
plete myomeres, and that 105 must develop themselves in 
relation to the 105 complete myomeres,—that is to say, between 
the fourth and fifth myomeres, between the fifth and sixth, and 
so on until we reach the 105th vertebra lying between the 
104th and 105th myomeres. I further conclude that seven 
other vertebra are developed at the caudal extremity, as indi- 
cated by the number of vertebral arches and the spinal ganglia 
in that region. We count, therefore, in all 115 vertebra, and 
this is the number which can be easily seen in many specimens 
of Anguilla vulgaris. 
1 Murenesox savanna is said to have 109 vertebre, but it is 
doubtful whether it really occurs in the Mediterranean. The position of 
its nostrils and the number of its branchiostegal rays render its association 
with Leptocephalus brevirostris impossible. 
