22 MONOGRAPH OF THE FRESH WATER III. 



ought to make the remark that the two posterior rays of the second dorsal have 

 been omitted in the engraving, and thus it is not sufficiently near to the base of 

 the caudal. The interhaemal spines are represented a little too much inclined, 

 so that, while the anterior edge of the anal fin is correctly situated, the anterior 

 interhaDmal spine ought to abut against the first caudal vertebra, thus three 

 vertebra) more backwards, instead of seeming apparently connected with the three 

 pairs of pelvic appendages, the extremities of which alone should abut against tin- 

 anterior interhacmal, leaving the latter behind them. The insertion of the ribs is 

 more correct than in C. viscosua, although the anterior pair should come higher and 

 reach the neural arch. The fins have been cut off from want of space. 



The skull (Plate III, Fig. 2225) exhibits that remarkable feature in the 

 structure of the genus Triglopsis which reminds us of Sciamoids, and consists in 

 the presence on the upper surface (Fig. 22), and on the face, of large mucus holes, 

 communicating directly with the lateral line. The general form of the cranial 

 box is elliptical, the upper surface smooth in the middle, flat, slightly dipping in 

 front. On both sides the mucus channel is open from the paroccipitals to the post- 

 frontals, into which it passes, until it meets its fellow of the other side, and takes 

 with it a parallel course through the fronto-orbital arcade to the snout. In fact, that 

 arcade is entirely transformed into a double channel whose walls are extremly thin and 

 semi-transparent. The turbinals are in their respective place on Fig. 2'2; the nasals 

 are not very conspicuous, and are covered in this case by the turbinals, which occupy 

 exactly the same position as in Acanthocottus (Fig. 2G), where the turbinals are 

 also united to the upper part of the snout. The cranial box itself is so thin as to 

 shrink in drying when all soft parts, internal and external, are removed. The 

 lower surface (Fig. 23) is very smooth ; the acoustic capsules are proportionally 

 large, although not very conspicuous on the figure, as they had shrunk since they 

 were prepared for the purpose of being drawn. In the profile view (Fig. 24) the 

 proportional length of the cranial box and the orbito-frontal arcade is very obvious ; 

 the former being shorter and less elevated near the orbit than on the occipital 

 region. 



A character belonging to the vomer (12) and which may vanish away during the 

 preparative process of the skull, is represented on Plate II, amongst the movable 

 bones of the head. This consists in the presence on the anterior and median line 

 of that bone, of a narrow elliptical band of teeth similar to those which exist on 

 the front of the same bone. 



The i>/-< }ii>i.ri//<u-i/ ('2'2) has the general appearance of an open triangle; its 

 ascending branch is shorter than the horizontal one ; and terminates in a point, 

 behind which there is a flat and much shorter process. The horizontal branch is 

 likewise expanded, although the very tip terminates in an acute angle. The mn.i-il- 

 l'ir;/ (21) is an elongated and curved bone, narrow on its middle, provided in I'ront 

 with a trifid articulating head, whilst its posterior extremity is flattened, truncated, 

 and movable into the membrane which forms the an^le of the mouth. 



The ji'ilniiiu' (20) is provided posteriorly with :v needle-like spine which extends 

 backwards in contL'iiity with the stylilorm pteryjroids. The entopierygoid (%&) is 

 blade-shaped and lias the transparency of the thinnest membrane. The 



