﻿ELONICHTHYS STRIOLATUS. 



59 



more strictly limited to the anterior part of the scale (fig. 14), the rest of the surface 

 being occupied only by scattered points, but it is never altogether lost even on the 

 sides of the tail. The posterior margin of the scale is sharply and delicately serrated. 

 Very prominent large scales are seen in front of the median fins (PI. VII, figs. 9 

 and 10). 



The paired fins are rather small compared with those of the species from Penton just 

 described, the pectorals equalling only two thirds the length of the head and the ventrals 

 scarcely half. Both are moderate in expanse and acuminate in form ; the number of the 

 pectoral fin-rays, which are closely articulated from their origins, is about twelve ; in the 

 ventral the number is probably rather less. The median fins are, however, powerfully 

 developed ; the dorsal is placed nearly opposite the interval between the ventrals and 

 anal, commencing a little behind the origin of the former and terminating a little behind 

 that of the latter. Both dorsal and anal fins are very similar in shape, being acutely 

 triangular, much elevated in front, and having the posterior margin concavely excavated ; 

 in both the length of the anterior rays exceeds that of the base of the fin ; the number of 

 rays in each may be estimated at about thirty, of which the fifth or sixth is the longest. 

 The caudal is very largely developed, deeply cleft and inequilobate, the superior lobe 

 passing upwards with a great sweep ; the lower is acutely pointed. The rays of all the 

 fins are remarkable for the excessive closeness of their transverse articulation, the joints 

 being broader than long, except at the commencement of the caudal. Here the rays, 

 forming about three fourths of the lower lobe, are for some little distance divided by more 

 distant articulations, the joints produced by which appear twice as long as broad, their 

 apparent length being proportionally increased by the greater amount of imbrication of 

 the demirays in this part. Likewise in the dorsal and anal, the articulations of the 

 commencement of the more anterior rays are not so close as over the rest of the fin, but 

 yet much closer than in the part of the caudal just referred to. Externally the ganoid 

 surface of the rays (PI. VII, fig. 6) is ornamented with delicate stria?, parallel with, or 

 slightly oblique to, the direction of their length. The longer rays of the anterior part of 

 each fin begin to dichotomise towards their extremities ; this division gradually creeps 

 up posteriorly till, in the short rays behind, it takes place about their middle ; the latter 

 condition is, of course, observable all along the upper lobe of the caudal. The fulcra are 

 closely set and minute, though at once obvious under an ordinary lens. 



Observations. — ffloniclithjs striolalus is one of a group of species, eminently charac- 

 teristic of the Lower Carboniferous rocks of Scotland, yet very well marked by 

 their moderately sized paired fins and their serrated delicately striato-punctate scales. 

 Some of them are rather difficult to distinguish from each other, but the present species 

 may be readily recognised by the extreme closeness of the articulations of its fin rays 

 and the moderate size and delicate ornamentation of its scales. 



Described as a " Palceoniscus " by Agassiz, the resemblances which this species bears 

 to two others referred by him to " Amblypterus," viz. A. nemqpterus and A. punctatus 



