24 MONOGRAPH OF THE FRESH WATER III. 



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

 The ntpraorbitnl we were at a loss to find. 



The hyoidean apparatus is composed of the usual bones. The small xti/l<>ln/<il 

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

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

 ostegals. The bas&yal and ylwsoliyal are seen, one in front, the other above- tin- 

 anterior extremity of the ceratohyal. The nr<>lii/<il (43) is provided with an elon- 

 gated membranous appendage underneath. The hnnn-li'mntegah (44) are cylindrical 

 and slightly curved. 



In the branchial arches, the small basibmnchials (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 /ii//><>l>r<tit<-/ii<i/x (-Hi) are 

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

 The ceratolii-iinfliidh (47) are very slender, slightly convex, provided on both sides 

 and inwardly with little tubercles beset with extremely minute teeth. The >/>!- 

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

 series. T\\Q pltarynrjdbranchial (49) is subquadrangular, the entire exposed surface 

 of which is covered with minute teeth. The !/>/< r/m- pharyngobrcmcMah (49') are 

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



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

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

 coracoid (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 ulna (54), the radius (55), and the carjxils (5C), 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 

 metacarpophalanyeals (57) articulate. 



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

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

 the metatarsophalaiujeah (70). The external and shorter om- is bony and unjointed. 

 whilst the three remaining ones are soft and jointed. 



The vertebral column is composed of thirty-nine vertebra*, 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 vertebne, 

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

 the vertical diameter of the middle of the body of the vertebra-, however, is greater 

 than the transverse. The neurapophyses and ha-mapophyses generally are quite 

 uniform, 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 (///). The numbers 1 to 1'J appended to the verte- 

 bi:e do nut indicate their rank in the series. Numbers 3 to 1 - are of natural si/.e. 

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

 the li_":iv- are altogether too small. Numbers 1. 'J and '', I elmig to the thoracic 



