SEMIOXOTIDiE. 
143 
A species equalling D.politus in size. Maximum depth of trunk 
somewhat less than its length (exclusive of the caudal fin) and a 
little more than three times as great as the depth of the caudal 
pedicle. Head with opercular apparatus occupying nearly one- 
quarter of the total length of the fish; the external bones orna¬ 
mented with rounded, sharply defined tuberculations of moderate 
size, sometimes elongated, rarely fused into short rugae. Marginal 
teeth large and unicuspid. Scales smooth, with few sparse punc- 
tations; the hinder border delicately serrated, the serrations 
becoming especially conspicuous in the middle of the caudal region. 
The form of the operculum is apparently not constant, but in 
most of the specimens assigned to D. punctatus it is relatively 
narrower and deeper than in the type species. 
Form. ^ Log. Lower Lias: Dorsetshire. Upper Lias : Wiirtem- 
berg. 
Unless otherwise stated, the following specimens were all obtained 
from the neighbourhood of Lyme Eegis :— 
19486. Imperfect head and trunk, wanting the greater part of the 
fins, but displaying the squamation. Purclias&ctI, 1845. 
35793. Well-preserved fish with imperfect fins. The operculum 
measures 0*045 in maximum depth and 0*03 in maximum 
width: the upper end is arched forwards, rounded, and 
tapering, and many of the superficial tuberculations are 
elongated. Purchased , 1860. 
36258. Another fine specimen relatively more elongated (apparently 
by distortion). The operculum is less deep in proportion 
to its breadth than in no. 35793, and there is more ten¬ 
dency to the elongation of the superficial tuberculations. 
The tubercles upon the cranial roof exhibit frequent fusion 
into continuous series. Purchased, 1862. 
P. 3554. Nearly complete fish 0*39 in length, with an operculum 
of the same form as no. 35793, more sparsely tuber - 
culated. The marginal teeth are unicuspid, and very 
long though robust. The scales of the lateral line exhibit 
crescentic perforations ; and there are traces of a superior 
lateral sensory canal, not perforating the scales it traverses, 
but passing through pairs of elongated tubercles. 
Enniskillen Coll • 
P. 2053. Imperfect large specimen in septarian nodule, labelled 
Tetragonolejois leachi by Agassiz. Egerton Coll. 
