PHOLIDOPHORIDJE. 
449 
some specimens. The right and left halves of the rays in the dorsal 
and anal fins are very loosely apposed, and their frequent displace¬ 
ment in the fossils renders it difficult to count them. 
The characters of Pholidophorus are remarkably constant through¬ 
out the Jurassic period, but most of the later species are more 
elaborately ornamented than those of earlier date. Some of the 
distinctive features of the species described below are enumerated 
in the following synopsis :— 
I. Scales not serrated. 
Length of head slightly less than maximum 
depth of trunk and contained five 
times in total length ; dorsal opposite 
pelvic fins; scales large and smooth, 
scarcely convex border, four deepened 
series ... bechei (p. 4-50). 
Stouter, with relatively larger scales .... pachysomus (p. 453), 
Smaller, differing in larger size of head 
which equals about one quarter of the 
total length. latiusculus (p. 454), 
More slender ; head occupying one-fifth ; 
dorsal arising behind peivic fins ; 
scales thinner, with convex hinder 
border .... stricklandi (p. 456). 
Somewhat stouter and head smaller; 
dorsal opposite pelvic fins; scales very 
thin, none much deeper than broad . . caudalis (p. 457). 
Head occupying one-fifth; dorsal opposed 
to pelvic fins ; scales coarsely but 
feebly rugose, and about six series 
deepened. germanicus (p. 459). 
Head occupying one-fourth ; dorsal arising 
behind pelvic fins ; fulcra remarkably 
large ; scales smooth, four series much 
deepened, especially that of lateral 
line . purbeckensis (p. 460). 
II. Scales serrated. 
Head occupying one-fourth ; dorsal opposed 
to pelvic fins; sparse denticulations 
on the four deepened flank-series of 
scales.= . . higginsi (p. 461), 
Very slender, and head occupying one-fifth ; 
dorsal arising behind pelvic fins ; 
scales scarcely deepened, partly ridged 
along lines of growth, and serrations 
coarse . .. crenulatus (p. 463). 
Stouter, with larger head ; scales smooth 
and more finely serrated, five series 
deepened on flank 
PAKT HI. 
limbatus (p. 464). 
2 u 
