14 MONOGRAPH OF THE FRESH WATER Til. 
CHAPTERWEL. 
ANATOMICAL OBSERVATIONS. 
§ 1. GENERAL REMARKS. 
Ir is not our intention in this place, to present the Anatomy of the Cottoids 
further than what may be necessary to the complete Zoological discrimination of 
the genera and species. Nevertheless, if we have given more anatomical detail 
than may be necessary for the above object, we would have this considered as so 
much towards a complete anatomy, which we trust may some day be furnished. 
§ 2. Tur Bony FRAME or Corrus VISCOSUS. 
Puate III. Fig. 1—9. 
The skeleton (Fig. 1), is intended to give a general idea of the internal frame. 
The first vertebra is concealed by the scapular; the first and eighth ray of the first 
dorsal fin are omitted by accident. 
The skull (Fig. 6—9), or that part of the head composed of the occipitals, parie- 
tals, frontals, mastoids, vomer, nasal, ethmoid, petrosals, and sphenoid, may be sub- 
divided into two regions. An anterior region composed of the vomer, nasal, eth- 
moid, prefrontals and part of the sphenoid constituting an arcade over the eyes, on 
both sides of which are the orbits. The posterior region is more bulky; it is the 
solid box which contains and protects the brain. 
Seen from above (Fig. 6), and below (Fig. 7), the general form of the cranial 
box is a little longer than wide, and the width behind, on the occipital region, is 
considerably greater than in front, near the orbits. The upper surface is smooth, 
a little depressed in the middle, whilst the occipital region is rather convex, 
(Fig. 9.) The profile (Fig. 8) shows more accurately the extent of the two regions ; 
the orbito-frontal arcade having exactly the same length as the cranial box; besides, 
we observe a character which is peculiar to C. viscosus, at least amongst the species 
figured on Plate III, that is the great convexity of that arcade. The same character 
is very likely to be found in all the species whose external features exhibit a very 
truncated snout, such as C. Alvordii, C. meridionalis, Xe. 
The movable bones of the left side of the face and head in general are represented 
isolated in Fig. 5". The premaxillary (22) has the form of a right angle; both of 
its branches being of equal length. The horizontal one is a flat ellipsoidal piece pro- 
