62 FISH GALLERY. 



are so attenuated as to have the form of tapering filaments, devoid 

 of scales and fin-rays. The red structures projecting as tufts from 

 the pelvic fins are highly vascular filaments which are developed 

 in the male during the breeding season, and doubtless act as 

 accessory respiratory organs ; they dwindle away after the 

 breeding season. These accessory breathing organs are not 

 altogether without parallel, for in a Siluroid fish, Plotosus, there 

 is a median, red, tree-like, branched organ, situated immediately 

 behind the anus and in advance of the anal fin. It is not clear in 

 the case of Plotosus whether the organ varies in size at different 

 seasons and whether it occurs in both sexes. 



The Lepidosiren occurs in the marshes and swamps of the 

 rivers of the central part of the South American continent. It 

 is of sluggish habits and feeds on water-snails and water-weed. 

 It rises to the surface to breathe, making use of the lung-sacs 

 as well as the gills ; in the dry season it remains iu a torpid 

 condition in the dried mud and breathes by the lungs alone. The 

 flesh is much esteemed as food by the Indians. A series of the 

 eggs and young of Lepidosiren, as also those of Protopterus and 

 Ceratodus, are exhibited in Cabinet-case 29 (specimens 1159, 1160, 

 1161). 



COCCOSTEOMORPHI (Jointed-neck Fishes). 



The Coccosteus-like fishes (Coccosteomorphi or Arthrodira) are 

 extinct fishes of the Devonian and Lower Carboniferous periods, 

 and are but doubtfully referred to the subclass Dipnoi. The head 

 and front portion of the trunk are covered with large bony plates, 

 the head plates being movably articulated upon those of the body, 

 whence the name Arthrodira (joint-neck). The teeth are some- 

 what similar to those of Protopterus. The vertebral axis appears 

 to have been unossified, but the dorsal and ventral arches and the 

 supports of the single dorsal fin are slightly bony. The tail is 

 heterocercal, and there are evidences of the existence of pelvic fins. 

 A restoration of Coccosteus decipiens, of the Lower Old Red Sand- 

 stone of North Scotland, is shown in two views, dorsal (180) and 



