778 MB. G. A. BOTJIiENGEB OS THE FISHES [NoV. 15» 



The sciagraph of Onathonemus rliynchophorus, which is appended 

 to this paper, shows well the three regions into which the vertebral 

 column may be divided, and also the so-called Gemmingerian 

 bones running parallel to the axis, dorsally to the neural spines, 

 and ventrally to the hfemal spines in that portion of the caudal 

 region which is occupied by the electric organ. These curious 

 ossifications, discovered by Gemminger, have been shown by 

 Hyrtl to be a universal character of the Mormyridce, though not 

 directly related to the electric organ. 



By a curious oversight, the Mormyridce have been referred by 

 Jordan and Evermann (Fish. N. Amer. i. 1896, p. 114) as an 

 Order {Scyplwpliori, Cope) to the group Ostariophysi, Sagemehl, 

 embracing the Silurido', Gymnotidce, Cyprinido', and Characinidxr, 

 which agree in the co-ossification of the anterior vertebra and 

 the connection of the air-bladder with the ear through the 

 Weberian ossicles. Such a character is well known not to exist 

 in the Mormyrs, which would fall under their definition of the 

 order Tsospondyli, Cope, but for the absence of the symplectic bone. 

 The nearest allies of the Mormyrs, giving an idea of the more 

 generalized type from which they may have been derived, appear 

 to me to be found in the Alhulidce, as suggested by Valenciennes 

 in 1846. These possible ancestors of the Mormyrs belong to the 

 most generalized forms of Clupeines, i. e. those most affine to the 

 Amioid Ganoids, having retained the muscular conus arteriosus 

 with two rows of valves, as first shown by Stannius in 1846 ; 

 whilst the nearly related lowly Clupeines, the Chirocenh-idce and 

 the Elopidce, are unique in the retention of two other ' Ganoid ' 

 characters, viz., the spiral fold of the intestine in the former, and 

 the gular plate in the latter. 



The family il/oc?n?/nf?<:e maybe defined as Isospondylous Physos- 

 tomes with coalesced prsemaxillary bones, parietals separating the 

 frontals from the supraoccipital', with a cavity on each side of the 

 pai'ietals leading into the interior of the skull and covered with a 

 thin lid-like bone, with the subopercular small, if present, and 

 without symplectic bone ^. Opercular bones concealed under the 

 skin ; gill-clefts narrow. 



These Fishes, of w'hich 73 species are described in this paper, 

 are restricted to the fresh waters of Africa, from the Nile and 

 Senegal to Angola, Lake Ngami, and the Zambesi. The Congo 

 has yielded more species than any other river, viz. 34. 



A great deal has been published on their anatomy and physiology ; 

 the principal contributions are recorded below. Unfortunately 

 nothing as yet has been observed on their breeding-habits and 

 development, and we do not know whether the young pass through 



^ Giintber's statement (Cat. ri. p. 214) " Single parietal bone " can only be 

 accounted for by a mis-rendering of Valenciennes's description (xix. p. 234) : 

 " En arriere des frontaux nous voyons deux petits pari^taux se toucher, comma 

 dans les carpes et comma dans les aloses, pour former une espece de plaque 

 impaire sur la voiite du crane." 



^ In the two latter points they agree with the Siluroids, to which they bear, 

 however, no relationship. 



