24 



72. The upper and lower jaws of a Siluroid fish of the genus Platystoma . it is attri- 



buted to the Silurus fasciatus of Bloch in the Osteological Catalogue of 1831. 

 The teeth are arranged on the premaxillary and premandibular bones in broad 

 bands like a rasp of strong short bristles. There are two small groups of 

 similar teeth on the vomer. 



Presented by Claude Russell, Esq., the executor of Dr. Patrick Russell, to Sir Joseph 

 Banks, Bart., and by him to the Museum of the College, 1805. 



73. The upper and lower jaws of the same species of Platystome (Pl.fasciatum). 



Presented by Sir Joseph Banks, Bart. 



74. The cranium, with the anchylosed anterior trunk-vertebrae, the tympanic pedicles, 



preoperculars, left opercular bone, and suprascapular bones, of a species of 

 Siluroid fish (Silurus (Schilbe) congensis, Leach)*; from the Congo River. 



This specimen is chiefly interesting as showing the close resemblance between the modifi- 

 cations by which the anterior abdominal or cervical vertebrae have deviated from the common 

 vertebral type, and those by which the cranial vertebrae more constantly deviate from the 

 same type. The bodies, for example, of three cervical vertebrae have coalesced into a con- 

 tinuous bony mass, grooved below : the parapophyses of two of the vertebrae are horizontally 

 expanded, and form a continuous plate like the paroccipitals (4), mastoids (e), and post- 

 frontals (it) in the skull. Two of the spinous processes have also coalesced to form a con- 

 tinuous longitudinal crista of bone, the summit of which expands laterally to an equal breadth 

 with the spines of the occipital, parietal and frontal vertebrae, and present a similarly granu- 

 lated outer or upper surface. The frontal is longitudinally fissured. The prefrontals send 

 down short obtuse articular processes for the suspension of the palato-maxillary arch. The 



* The following are the specific characters of this fish, given by Dr. Leach in the Appendix No. 4 

 to the " Narrative of an Expedition to explore the river Zaire, usually called the Congo, in South 

 Africa, in 1816; by Captain J. N. Tuckey, R.N." 



" Sp. 1. Silurus congensit. With the upper nostrils, the angles of the mouth, and each side of the 

 chin furnished with a filament ; the first ray of the dorsal and pectoral fins serrated towards the point, 

 which is unconnected with the second ray ; the second ray very much elongated and attenuated ; the 

 laciniu; of the tail acute. 



" Obt. The first ray of the dorsal fin is only serrated towards its point, the unconnected apex itself 

 being destitute of teeth. The first ray of the pectoral fins is serrated above the unattached part, an 

 the teeth are continued downwards to near its middle. It is akin to Silurus mystus (Geoff. Poiss. de 

 Nil), but may be easily distinguished from it by the characters of the pectoral fins, and by the presence 

 of the filaments on the chin. The filaments of the chin and nostrils are nearly of equal length ; those 

 of the angles of the mouth are very long." 



