314 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



arising from the anterior and inner region of the basal 

 portion. At the posterior and outer corner of the large 

 basal segment is the operculum (op.), which covers the 

 external excretory opening. This operculum probably 

 represents the co.vo podite and the larger basal portion the 

 basipodite, the two together forming the protopodibe. The 

 flagellum probably represents the endopodite. 



The outer edge of the basipodite is fused to the sub- 

 hepatic region of the carapace. Backward processes from 

 the supraciliary (S.l.) and supra-orbital lobes fuse with 

 the anterior end of the basipodite. The inner and 

 posterior corner of this segment is in contact with the 

 lateral portion of the first sternum, and the posterior 

 border of the same segment is in contact with the 

 epistoma. 



The Mandible (PL II, fig. 6) lies at the side of the 

 mouth. The main portion is an elongated strongly 

 calcified structure which is divided into two parts — an 

 inner part, which projects over the ventral region of the 

 mouth, and acts as the " jaw," and an outer part, the 

 apophysis (apoph.), to which are attached the tendons of 

 the mandibular muscles. At the outer extremity is the 

 tendon of the external adductor (t.ex.ad.). Behind this, 

 attached to a small projection, is the tendon of the 

 external abductor (t.ex.ab.). To the posterior and inner 

 side of the apophysis is attached the tendon of the internal 

 adductor (t.int.ad.). The internal abductor arises from 

 the apophysis on the inner side of the base of the tendon 

 of the external adductor. There is no tendon for the 

 internal abductor. Anteriorly the mandibular palp (md. 

 palp.) arises from the inner side of the apophysis. The 

 mandible is hinged to the epistoma by means of a small 

 projection below the palp. There is no definite hinge 

 posteriorly, but the posterior border of the inner region 



