18 MONOGRAPH OF THE FRESH WATER Ill. 
skin of the thoracic region. It has nearly twice the size represented on the figure. 
There is no bone in the scapular arch which we can homologize with the humerus 
unless the so-called epicoracoid should answer for it. Indeed, we cannot help 
thinking that this styliform, rib-like bone (the epicoracoid) is the humerus itself, 
which having no part to perform in the plan of structure of Cottoids and others, 
has lost its primitive shape to assume that of the lowest production of the bony 
frame, a pleurapophysis, or a dermal spine. The ulna (54) above, and radius (59) 
below, having between them the carpals (56), three in number, build up a thin 
osseous band fixed by one edge to the convexity of the coracoid, whilst to the other 
edge the rays of the pectoral fin, the metacarpophalangeals (57), articulate. 
The ventral fins (Fig. 5"), are attached to the scapular arch itself, immediately 
under the head. The pubic bones (63) are elongated, subtriangular, in close con- 
tact with each other, and penetrating forwards between the coracoids, above the 
junction of these latter bones. Their central portion is very thin, whilst the edges 
are stout, the outer one sharply carinated. The rays or metatarsophalangeals (70) 
articulate immediately on the posterior extremity of the pubic bones. The outer 
one is a hard and unjointed spine, the head of which is lodged in a notch of the 
pubic bone. The other rays, the true metatarsophalanges, three in number, are 
soft and jointed. 
The vertebral column is composed of thirty-one vertebra, eleven of which are 
abdominal, (eight thoracic, three pelvic,) and twenty caudal. There are eleven 
pairs of ribs attached to the abdominal vertebrae; the pelvic vertebra, in addition 
to the ribs, have suspended underneath, a pair of slender rib-shaped bones, very 
much inclined backwards. The centra of the thoracic vertebrae are subcircular, 
possessing only neurapophyses, which constitute a semi-lunar neural arch, of con- 
siderable development (Fig. 5’). Some of them may occasionally exhibit minute 
knobs on the sides, indicating the situation of the parapophyses. The seventh 
and eighth vertebre show the first rudiment of haemapophyses; their neural arch 
has become narrower and higher. The neural spines (” s) are intimately soldered 
with the neural arches throughout the whole length of the vertebral column. 
The anterior pair of ribs is inserted at the basis of the neural arch itself, above 
the body of the vertebra, with its extremity fixed to the scapular arch by means 
of ligaments; the following pairs are merely kept within the fleshy walls of the 
abdomen, whilst their point of attachment to the vertebrae is gradually lower and 
lower till it takes place on the hemal process of the pelvic vertebrae, after having 
passed through all the intermediate steps from the neural arch above. Figs. 30 
and 31 exhibit the insertion of the first and last ribs of Acanthocottus virginianus ; 
their larger size permits the illustration of this fact better than in the case of C. 
viscosus. The three pelvic vertebrae of C. viscosus are represented in Fig. 5° (4) in 
connection with two caudal ones. Under the middle one, and detached from it, is a 
pelvic appendage, the insertion of which is shown in the case of the tenth vertebra 
(«) having immediately above it the pair of ribs, the last but one of the series. 
The neural canal is growing narrow and high, diminishing gradually towards the 
tail (¢). The neural arch and neural spine (7 s) become more erect and more 
slender (compare 6 with e). The caudal vertebrae, when seen in profile, appear 
