( 9 ) 



thus. Scyphax also, judging from the figures, belongs to here ; it may, 

 however, form a distinct type, as the coxob of the second appears to be 

 developed. The animal figured by Dana as the young of this genus can 

 scarcely be so, unless it be an exception to all the rules which regulate 

 the form of the young in this family. He has himself proposed to call 

 it Actajcia. 



4. Coxfls present in second, third, fourth, and fifth rings, the sixth 

 reduced to its minimum : Armadillo, Sphajrillo. 



11.— The Form of the Head. 



"We shall next examine the arrangement of the various parts of the 

 cephalic segment, or, as I have called it, the head ; these are of minor 

 importance, but still assist much in classification. It will be necessary 

 to examine the native genera in detail. 



Ligia, Plate XX., Figs. 7 to 10. 



When the head is looked down on from the front, we remark an- 

 teriorly just beneath but not attaining to the frontal line of the head, 

 a broad plate extending over the entire forehead, and divided transversely 

 by a raised ridge ; its superior margin also marked by a raised ridge. 

 This superior ridge passes off on each side beneath the eyes, forming at 

 least a third of the inferior border of the orbit. The extemtd angle of 

 the orbit, however, is formed, not by this, but by the cephalic ring con- 

 tinued forwards from behind, and terminating as a rounded knob just 

 above the external antenna? ; these arise in the angle between the in- 

 ferior border of the frontal plate and the projecting lobes. The inferior 

 border of the frontal plate is formed of two curves, convex upwards, one 

 over the origin of each external antennae ; the angle of their jimction is 

 truncate, separated by a short transverse suture from a small, narrow, 

 somewhat quadrilateral plate, which bears the internal antennae, and is 

 probably the remains of the second or internal antennary ring, the frontal 

 plate itself representing the external antennary or third ring of the 

 tjrpical crustacean; beneath this is a broad, well-marked plate, the 

 epistome. 



Philoscia. Plate XX., Figs. 1 to 6. 



The inferior border of the frontal ring is nearly straight across, the 

 transverse suture well marked, nearly on a level with the superior mar- 

 gin of the external antenna), its superior margin curved, raised, and 

 passing slightly beyond the frontal line of the cephalic segment, shutting 

 out the orbit from the insertion of the external antenn®, and a deep sul- 

 cus separating it from the external angle of the orbit, the third ring 

 being thus transverse and narrow. The second ring is nearly as deep as 

 the third, and well marked ; the epistomal plate narrow, and formed of 

 two triangles placed apex to apex. The orbits are open below and be- 

 hind. 



