18 MONOGRAPH OF THE FRESH WATER III. 



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 humcrus 

 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 ulnn (-34) above, and r<t<lui* (>>) 

 below, having between them the carpal* (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 mdltearptpkaitmyealt (~>7), 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 meiatarsop1i<il:n.iil8 (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 1 , 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 vertebra) are subcircular, 

 possessing only neurapophyses, which constitute a semi-lunar neural arch, of con- 

 siderable development (Fig. 5' /3). Some of them may occasionally exhibit minute 

 knobs on the sides, indicating the situation of the parapophyses. The seventh 

 and eighth vertebrae show the first rudiment of hacmapophyses; their neural arch 

 has become narrower and higher. The neural spines (n ) are intimately soldered 

 witli 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 vertebra) is gradually lower and 

 lower till it takes place on the haemal process of the pelvic vertebra), 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 Acantln-<>ltuK rinjinininu ; 

 their larger size permits the illustration of this fact better than in the case of ('. 

 visoosus. The three pelvic vertebra? of C. visoosus are represented in Fig. 5' (<?) in 

 connection with two caudal ones. Under the middle one, and detached from it, is a 

 pelvic appendage, the insertion of whicli is shown in the case of the tenth vertebra 

 () h:iviii;r immediately above it the pair of ril>s, the last but one of the series. 

 The neural canal is growing narrow and hidi, diminishing -nulually touanls tin- 

 tail (i). The neural arch and neural spine (n a) become more erect and more 

 slender (compare with f). The caudal vertebra-, when seen in profile, appear 



