24 MONOGRAPH OF THE FRESH WATER III. 



the latter into the nasal cavity, thus meeting the suborbital branch on the snout. 

 The supraorbital we were at a loss to find. 



The hyoidean apparatus is composed of the usual bones. The small stylohyal 

 (38) is nearly straight; the epiliyal (39) subtriangular, bearing two branchiostegals. 

 The ceratohyal (40) is the longest, and attached to it are the four remaining branchi- 

 ostegals. The hasihyal and (jlossohyal are seen, one in front, the other above the 

 anterior extremity of the ceratohyal. The urohyal (43) is provided with an elon- 

 gated membranous appendage underneath. The hranchiostegals (44) are cylindrical 

 and slightly curved. 



In the branchial arches, the small hasibranchials (45) are scarcely to be distin- 

 guished, this series of bones forming a cartilaginous band in the midst of which 

 minute surfaces of ossification alone are discernible. The JiypohrancMals (46) are 

 independent from each other, short, thin, and flattened, varying somewhat in shape. 

 The ceratohranchiah (47) are very slender, slightly convex, provided on both sides 

 and inwardly with little tubercles beset with extremely minute teeth. The epi- 

 hrancliials (48) are the most variable of all the bones constituting an homonyme 

 series. The pJiaryngobranchial (49) is subquadrangular, the entire exposed surface 

 of which is covered with minute teeth. The ivferior pharyngohravchials (49') are 

 elliptical and beset with teeth similar to those of the pharyngobranchials. 



The svpra-scapukiT (50) is as usual, situated above the paroccipito-mastoid groove; 

 but its centre is hollow. The scapular (51) is subtriangular, thin and flat. The 

 coraccdd (52) is likewise very thin, flattened upon different planes, and crescentic. 

 The epicoracoid (58) is styliform and a little longer than represented on the figure. 

 The iilna (54), the radius (55), and the carjmls (56), are altogether in a cartilagi- 

 nous state. The ulna and radius are contiguous and form a band along the cora- 

 coid, thus preventing the carpals from coming into contact with the latter. The 

 carpals themselves are surrounded by a thin semi-membranous edge, on which the 

 Tuetacarpophalangeals (57) articulate. 



The ventral fins are connected with the lower part of the scapular arch. The 

 puhic bones (63) are subtriangular, furnishing posteriorly a point of attachment to 

 the metatarsophalangeals (70). The external and shorter one is bony and unjointed, 

 whilst the three remaining ones are soft and jointed. 



The vertebral column is composed of thirty-nine vertebrce, twelve of which 

 belong to the abdominal region, and twenty-seven to the caudal. Accordingly, 

 there are twelve pairs of ribs corresponding to the twelve abdominal vertebrae, 

 three of them being provided with pelvic appendages. The centrum is circular; 

 the vertical diameter of the middle of the body of the vertebrae, however, is greater 

 than the transverse. The neurapophyses and hsemapophyses generally are quite 

 unifoi'm, slender, and little prominent. The neural spines [n s) are scarcely apparent 

 on the anterior thoracic vertebra (1, 2). The same enlarged figures exhibit the 

 peculiar shape of the neural arch seen from behind (1) and in profile (2), together 

 with the insertion of the ribs [pT). The numbers 1 to 12 appended to the verte- 

 brae do not indicate their rank in the series. Numbers 3 to 12 are of natural size, 

 and were intended to illustrate their special structure all along the column ; but 

 the figures are altogether too small. Numbers 1, 2 and 3 belong to the thoracic 



