110 CLASS XIV. 



membrane with 10 11 rays. Scales large. Pectoral fins elongate. 

 Caudal fin forked, with inferior lobe larger. 



Flying fishes. In some species the pectoral fins are as long as the body j 

 by means of these long fins these fish can keep themselves for a time above 

 the water. (See above, p. 51). They are all marine fishes, of which more 

 than thirty species are now known, though LINN.EUS recorded two of them 

 only, namely Exocoetus volitans L., (Cuv. et VALENC. Poiss. xix. PI. 559), 

 principally in the Mediterranean Sea, and Exoc. evolans L., BLOCH Ichth. 

 Tab. 398, occurring in the North Sea, the Atlantic, and also in the 

 Southern Pacific. 



Family XIX. Mormyrini. Upper margin of mouth formed 

 by the intermaxillary and supramaxillary bones; mouth small; 

 teeth in intermaxillary bone and lower jaw compressed, small, 

 emarginate or tricuspid; teeth in vomer and tongue subulate, 

 crowded. Branchial aperture small, linear ; branchiostegous mem- 

 brane with few (5 6) rays. Body compressed, covered with small 

 scales ; head with naked thick skin. Dorsal fin single, often long. 

 Swimming-bladder simple, furnished with a duct. 



Mormyrus L. 



Fresh-water fishes from Africa, of which several species are now 

 known. They differ from the fishes of the preceding family by a 

 longer intestinal canal, and two blind tubes (appendices pyloriccc). 

 At the posterior margin of the mastoid bone (see above, p. 20,) 

 there is a large oval aperture, which was discovered by HEUSINGER 

 in Mormyrus cyprinoides, and which is covered by a scale-like os 

 supratemporale (see above, p. 22 note) ; under the opening lies the 

 sac of the vestibule. 



See MECKEL'S Arckiv fur Anat. u. Physiol. 1826, s. 324 327, Tab. iv. 

 figs. 8io. 



At the tail, which is thickened, are situated on each side under the 

 lateral muscle two elongate organs, which cause the thickening, divided 

 into a number of spaces, and probably to be regarded as electric organs, 

 although, as far as I know, nothing has yet been ascertained respecting the 

 electric power of these fishes. 



ERDL and GEMMINGER observed this arrangement in Mormyrus oxy- 

 rhynchus and M. dorsalis, KOELLIKER in Mormyrus longipinnis RUEPPELL ; 

 see KOELLIKER' s description with figures, Berichte von der Tcbnigl. Zooto- 

 mischen Anstalt zu Wurzburg, n. 1849, 8 - 9 1 3- See a ^ so J- HYRTL, 

 Anatomische Mitiheilungen uber Mormyrus und Gymnarchus, Wien, 1856, 

 4to. Mit 6 Tafeln. (xii. J3d. der Denlcschr. der math, natur. Clause der 

 Kaiserl. A bad. der Wissensch.) 



HYRTL has figured remarkable diverticuU at the bulb of the arterial stem 

 of the gills. 



