Class 2. Pisces. Order 4. Dipnoi. 387 



2. Proiopterus anneetens, tlie African Limg-fisli, lias very long, thin limbs ; 

 it possesses some small, thread-like membranous appendages at the npper ends of 

 the gill apertures ; these possibly have a respiratory function ; the gills of the 

 fii-st and second arches are absent. In other external respects it is similar to 

 Ceratodus. If the water in which it is living di-ies up, it buries itself in the 

 ground, and suiTOimds itself by a hard mucous capsule, in which it can remain 

 for a long time without water (this is not the case with Ceratodus). An allied 

 f oi"m {Lepidosiren pa/radoxa) occurs in S. Ameiica. 



Order 5. TeleOStci. 



The skeleton consists of cartilage and bone ; chiefly the latter. 

 The conus arteriosus is rudimentary, a bulbus arteriosus is present. 

 There is no spiral valve in the intestine ; the operculum is bony ; 

 there is no spiracle ; the skin is provided with scales or bony 

 knobsj plates, etc. ; dermal denticles are usually absent, but may be 

 present in small numbers. The fins can be folded and are provided 

 with bony rays. 



Sub-Order 1. PhySOStomi. 



Swim bladder connected with the alimentary canal by a 

 pneumatic duct ; pelvic fins far back, close to the anus ; spinose rays 

 usually absent ; scales cycloid. 



1. The Herring family {Clupeidas). Body elongate and compressed; 

 large, easily deciduous, cycloid scales; only one dorsal fin; teeth feeble. To 

 this family belong: the Herring (Clupea harengus), and the. Sprat 

 (CI. sprattiis) ; the Sardine [CI. pilchardus); the Shad, [CI. alosa) all 

 common on British coasts ; the last makes its way into rivers [e.g., the Sevei-n) 

 to spawn ; all these very similar forms have a row of carinate scales along the 

 ventral side. The true Anchovy {Engraulis encrassieholus), without these 

 modified scales, and with elongate snout : in the MediteiTanean, occasionally in 

 northern seas. 



2. The Salmon family (Salmonidse). Scales small, or of medium size. 

 Two dorsal fins, of which the posterior is rayless and adipose. Chiefly in fresh- 

 water. Amongst the species occurring in the British Isles : the Salmon 

 (Salmo solar), marine, migrating into rivers to spawn; the closely-allied 

 Common Trout (S. /ario), in fresh water; the Sea- or Salmon-trout 

 (S. trutta) : the Char (sub-genus, Salvelinus), in mountain lakes. The species 

 of Goregonm (0. thymallus, the Grayling; C. pollan, the Fresh-water 

 Herring;) are edentulous, or have only smaU teeth, whilst the genus, Salmo, 

 has large ones. 



3. The Pike family {Esocidx). Small scales; dorsal fins far back; 

 flattened, elongate snout; mouth large, with numerous teeth; some of them 

 large. Few species ; the common Pike [Hsox limius), abundant in fresh water. 



4. The Carp family (Cyprinidsi). Body compressed, with larger or 

 smaller scales; one dorsal fin; bones of the mouth entirely edentulous 

 the lower pharyngeal bones are, however, provided with powerful grindino'-teeth, 

 which work against a thick horny plate on the under side of the skull ; usually 

 barbules on the edge of the mouth; freshwater fish, feeding partly upon 

 decayed plants. Of the numerous forms, may be mentioned : the Carp {Cyprinus. 



c c 2 



