332 WOODWARD : fossil fishes of the upper lias of WHITBY. 
Brit. Mus., No. P.5223, is exactly similar in character to that of the 
dentary, but comprises only eight teeth (pi. xlvi, fig. 4). 
Two of the best-known specimens displaying the general pro- 
portions of the fish are shown of one half the natural size in pi. xlviii. 
The first of these (Brit. Mus., No. P.3528) is exposed from the left 
ventro-lateral aspect, exhibiting the head and parts of all the fins, 
except the dorsal. The second (Brit. Mus., No. P.3527) is exposed 
in direct side view, displaying the greater part of the squamation in 
undisturbed order. 
The head of the first of these two fishes (fig. 1), though very 
imperfect, is interesting as confirming some of the observations 
made above in reference to the other skulls. Being a small fish, 
the cranial and cheek-plg-tes are very slightly tuberculated, while the 
opercular apparatus is quite smooth, as usual. The deepened 
posterior suborbital is preserved on both sides, and the normally 
single plate adjoining its lower border on the left side is here 
divided into two by a transverse suture, as in No. P. 74 10. The 
lowermost suborbital appears as usual. The characteristic maxilla 
is seen on both sides, but the premaxillae are broken away. The 
rami of the mandible (md.), viewed from beneath, exhibit the 
characteristic inward curve at the symphysis, and between them one 
of the ceratohyal bones seems to be exposed, very narrow in front, 
considerably expanded behind. Below the opercular apparatus on 
the left side, there are also remains of about four branchiostegal rays, 
the uppermost relatively large and broad. Parts of both pectoral 
fins (pet.) are shown, comprising stout and slightly -arched rays, 
which are undivided for more than half of their length, but are cleft 
distally into very fine jointed filaments. About thirteen of these 
rays are indicated in the left pectoral, but the series preserved is 
probably not complete. Both pelvic fins (pk).) are also imperfectly 
shown, and these seem to be about two-thirds as large as the pec- 
torals. Their rays are similar, but only about six or seven in number ; 
and there are traces of the series of slender fulcra on the anterior 
border of the fin of the right side. The distance between the origin 
of the paired fins is somewhat less than twice as great as that 
between the pelvic pair and the anal fin ; while the latter (a.) seems 
