850 CRUSTACEA. 



The area I, below the epistome, consists of an upper and lower part, 

 it being divided transversely by a suture crossing it with a curve 

 convex downward ; this suture is much less distinct than that sepa- 

 rating the labruni from the epistome. 



In order to compare these parts with those corresponding in the 

 Brachyura, the reader should refer again to figure 9 d, Plate ,11, and 

 to the description on pages 23 and beyond. It is there shown that 

 anterior to the mandibles, there is what is called the praelabial plate 

 and epistome ; and that the posterior part of the so-called epistome, is, 

 in fact, but a part of the praelabial plate, while the anterior part is 

 normally distinct and the true epistome ; the posterior part with the 

 anterior part of the praelabial plate is the segment pertaining nor- 

 mally to the second antennae ; and the anterior part represents the first 

 antennary segment ; also, the outer part of the praelabial plate and 

 the so-called epimerals (or lateral pieces) of the Brachyural carapax 

 correspond to the mandibular segment. 



In the Orchestia, the plate, d, appears to be part of the second 

 antennary segment or annulus, judging from its connexion with the 

 base of the second antennae. 



The epistome, e, lies between the two plates, d, and may be the 

 sternal portion of the same annulus. The piece /, as it is continuous 

 with the lower angles of e, appears at first to be of the epistome 

 annulus. But this would make the epistome normally posterior to 

 the second antennary annulus, as it is posterior to d, which is beyond 

 doubt second antennary. Moreover, / is evidently mandibular, as it 

 supports the base of the mandible. Hence as d stands against e, the 

 first view, making the epistome antennary, is most probably correct. 



The piece / terminates anteriorly at the upper lip (Z) as well as 

 against the lower angles of the epistome ; and if/ is mandibular in its 

 relations, we should thence conclude that the labrum (I) also pertains 

 to the mandibular annulus. The deep suture separating it from the 

 epistome (e) is sufficient reason for considering the two as pertaining 

 to distinct annuli. 



The maxillipeds are supported on a piece, .n, the back piece of the 

 lower part of the head [p) . n is, therefore, the proper episternal of 

 the maxilliped annulus, and^> the continuation of the segment. The 

 maxillae segments are not represented, unless combined with the 

 maxilliped segment in the part p. The piece h is the proper base 

 of the inner maxillae. 



