WOODWARD : FOSSIL FISHES OF THE UPPER LIAS OF WHITBY. 169 
The trunk of tlie fish to which these heads belong is still too 
imperfectly known for satisfactory comparison with P. macropterus, 
and they are only retained provisionally separate from the last- 
mentioned species because they seem to exhibit a slightly shorter 
snout. 
Explanation of Plates, 
Plate XIX. 
Fig. Page. 
1. Catiu'us sp. ind. ; left lateral aspect of head and opercular 
apparatus, br., branchiostegal rays ; c.o. (1 and 2)., 
circumorbitals ; 7nd., mandible ; ?;2.r., maxilla ; op., 
operculum ; p.cl., postclavicular scales ; p.op., pre- 
operculum ; p.t., post-temporal ; s.mcr., supramaxilla ; 
s.o. (1 and 2)., suborbitals ; s.op., suboperculum ; s.f., 
snpratemporal. [Whitby Museum.] ... ... 155 
Right post-temporal plate of same specimen. ... ... 155 
2. Catiirus sp. ind. ; lower aspect of head, etc. ag., angular ; 
br., branchiostegal rays ; d., dentary ; gn., gular 
plate ; ])ct., pectoral fin ; s., scales. [York Museum.] 157 
2a. Mandibular teeth of same specimen, twice natural size. 157 
2b. Upper flank-scales of same specimen. ... ... 157 
Plate XX. 
1. Saurostomus esocimis, Agassiz ; head and opercular ap- 
paratus, right lateral aspect, two-thirds natural size. 
ag., angular ; d., dentary ; hm., hyomandibular ; mx., 
maxilla ; op., operculum ; p.op., preoperculum ; r., 
crushed rostrum ; scL, sclerotic. [P. 3708.] ... 159 
1«. Anterior upper teeth of same specimen, seen from front 
aspect. ... ... ... ... ... 160 
2. Saurostomus esocinus, Agassiz ; pectoral fin, two-thirds 
natural size. [P. 3709a.] ... ... ... 160 
Plate XXI. 
1. Pachyconnus curtus, Agassiz ; right lateral aspect of fish, 
slightly distorted. [P. 3710.] ... ... ... 163 
