350 GENUS SQUILLA. 



lateral portions of which are formed as usual by the appendages of 

 the sixth segment ; the basilary joint of these is very robust, and 

 is prolonged into a long pointed scale, which stretches out beneath 

 and between the two terminal branches. 



It has been observed by Dr. Milne Edwards, that the 

 distinctness and separation of the normal segments, espe- 

 cially those of the head and thorax, are carried further in 

 this family than in any other form amongst the Crustacea ; 

 and in this view it may be considered as offering the 

 nearest approach to the typical structure, and the key to 

 the homologies of the class. Some further allusion to this 

 circumstance will be found in the introduction, and it will 

 be sufficient here to refer the reader to the descriptions 

 given by the excellent author just named, of the characters 

 of the family, and of the different genera ; and, in connexion 

 therewith, to the plates in which the details of the external 

 anatomy are given.* The species of the family are very 

 widely distributed; and even of the genus Squilla, the 

 coasts of Europe, Asia, Africa, and America, furnish ex- 

 amples. Of the three species which are known to inhabit 

 the Mediterranean, two have now been found upon our 

 South-western coast, both first discovered by the acute and 

 indefatigable researches of Mr. Couch. 



In the characters given above I have included those 

 which are most characteristic of the family of Squilladse, 

 as well as those which are distinctive of the genus, as this 

 is the only generic representation of the family indigenous 

 to Britain. 



* Hist. Nat. des Crust. II. p. 509 et scq. pi. 1, &c- 



