104 CRUSTACEA. 



This subgenus leads us to those in which these organs are formed 

 of granules or approximated simple eyes, and that also have the 

 four antennse, composed of four joints at most, inserted on one hori- 

 zontal line, and all the feet fitted for walking. The tail consists of 

 six segments, the last of which is large and suborbicular. Such is 

 the 



Limnoria, Leach. 



The only living species known is the Limnoria terebrans, 

 Leach, Edinb. Encyclop., VII, p. 433; Desmar., Consid., p. 

 312. Although scarcely above two lines in length, its habits 

 and fecundity render it highly noxious. It perforates the tim- 

 bers of ships in various directions and with alarming rapidity. 

 When taken in the hand it rolls itself into a ball. It is found 

 in various parts of the British seas. 



The figure and description of a small fossil crustaceous ani- 

 mal has been sent to Count Dejean by Professor Germar, which 

 seems to us to belong to this subgenus(l). 

 The third section Sph^eromides, Lat. exhibits four very dis- 

 tinct, short, setaceous or conical antennse, and a single genus An- 

 thura excepted, always terminated by a stem divided into several 

 small joints; the inferior, always the longest, are inserted beneath 

 the under part of the first joint of the superior which is broad and 

 thick. The arrangement of the mouth is as usual. The branchiae 

 are vesicular or soft, exposed, and arranged longitudinally in pairs. 

 But two complete and movable segments are observed in the tail, 

 the first, however, frequently presents impressed and transverse 

 lines indicating vestiges of others; on each side of its posterior ex- 

 tremity is a fin terminated by two leaflets, of which the inferior alone 

 is movable; the superior(2) is formed by an internal prolongation 

 of the common stem. The branchial appendages are curved in- 

 wards; the inner side of the first are accompanied, in the male, by a 

 small linear and elongated projection. The anterior part of the 

 head situated beneath the antennse is triangular, or has the figure of 

 a heart reversed. 



Some have an oval or oblong body, usually assuming, when con- 

 tracted, the form of a ball; the antennse terminated by a pluri-articu- 

 lated stem, and the inferior, at least, visibly longer than the head. 



(1) The Oniscus prsegustator, figured in Parkinson, is allied to this species, or at 

 least appears to belong to the same section. 



(2) It folds over the posterior edge of the last segment, and in several, such as 

 the Zuzarae, and Naess, Leach, like an arch. 



