Description of Genera and Species. 39 



Galathea. It might be argued that the Coal Measures form inhabited I'resh water, while 

 the Lower Carboniferous forms were marine ; but the fact that Anthrapalcemon qrossarti 

 is found associated with such marine forms as Lingula and Conularia has been long 

 known.' 



Family PEKIMECTURID^. 



Remarks. — This family is made to include the members of a group of Mysidian 

 Schizopods, believed to be intermediate between the Lophogastridaj and the Anaspida^, 

 conspicuous on account of the massive character of their tails in which they simulate 

 the modern Squillids. 



Genus PEPJMECTURUS gen. nov. 



Generic Characters. — Large forms with elongated and slightly applanated bodies; 

 integuments firm and smooth, or only slightly granulated. Trunk shorter than tail : 

 last seven trunk segments free, or only slightly attached, forming complete rings and 

 bearing massive limbs ; and in the females brood pouches on the hindmost segment. 

 Carapace with movable rostrum and with or without longitudinal keels, not 

 directly attached to last seven trunk segments, but covering them loosely and leaving 

 visible portions of the last two in the emargination of its posterior border. Tail very 

 largelj' developed ; segments well formed with overlapping epimera, well facetted for 

 rolling, and usually strengthened with transverse bars and often with longitudinal keel 

 and spines. Telson cordate and ending in strong hastate median spine. External branch 

 of uropods greatly developed and strengthened on outer side by blade-like keel set along 

 its outer edge with a row of articulated spines. 



Remarks. — The characteristic feature of the genus is the enormous develop- 

 ment of the tail. The flattened body of the relatively shorter and broader species 

 usually causes their members to be fossilised so as to expose the dorsal parts 

 only, so that the sterna and ventral organs are usually hidden, as the integuments are 

 too firm to allow them to show through. Fortunatelj-, however, these animals 

 shared, with Mysis (pi. vi., fig. 8) and other recent and pateozoic Schizopods, in tlie 

 habit, on dying, of flexing the body at the articulation in front of the la.st seven trunk 

 segments till the axis of the head organs and the carapace made a considerable angle 

 with that of the trunk segments (pi. vi, figs. 2, 4, 5). At the same time, the limbs are 

 all folded forwards close under the trunk, the distal joints of the legs being flexed back 



' J. W. Salter, Quart. Jomn. Ceol. Soc, 1861, vol. .wii., p. 530. 



