438 DISTRIBUTION IN SPACE AND TIME 



{Cal/iojiyums), and, in warmer countries, the little Mud-Skippers 

 \Periophthalmit,s and Boleophthalmus), the habits of which have 

 already been noticed. Other families are those which include 

 the Blennies {Blenniida-), many of the Bull- Heads {Cottid(X), and 

 the gorgeously tinted Wrasses {Labridtx). There are also the 

 curious Pipe -Fishes {Syngnathida:), remarkable for the brood- 

 pouch possessed by the male, and among these are the Sea- 

 Horses {Hippocampus, Phyllopteryx, &c.), which are not found 

 in British seas. 



Pj-iuiitive Vertebrates {Protochordata) of the Neritic Zone. — 

 Lancelets [Amphioxiis) and Acorn-headed Worms [Balanoglossns) 



Fig. 1292. — Coral-Fiih [Epinc/'hehts ht!j:a^onatiis) 



are widely distributed neritic forms, with burrowing habits. The 

 zone is also inhabited by large numbers of Ascidians or Sea- 

 Squirts {Urochorda), some solitary and some colonial, which in 

 their adult stage are attached to various objects. 



Neritic Molluscs [Mollusca). — Head-footed Molluscs (Cepha- 

 lopoda) abound in shallow water. Squids and Cuttle- Fishes, for 

 instance, being found in large numbers around our own coasts, 

 while eight-armed forms, such as the Poulpe {Octopus^ and its 

 allies, belong as much to the Benthos as to the Nekton, of the 

 Neritic region, for they crawl as much as they swim, or possibly 

 more so. 



Sea-Snails and Sea-Slugs {Gastropoda) simply swarm both 

 in shallow water and between tide-marks, especially in the tropics. 

 Among the commonest littoral forms on the British coasts are 

 the Limpets {Patella), which adhere so closely to the rocks that 

 they defy the wash of the tide, to which their conical shell affords 

 but little purchase; the Purple-Shells {Purpura lapillus), well 



