CRUSTACEA. 

 430 



illustration, to figures of Pagurm puwtulat^ and JSgUa, on Plate 28, 



and species of Galathea, on Plate 30. g 



In the Galathea it appears that the dorsal transverse suture is 

 only indicated by a faint depressed line, and may be wholly wanting; 

 and the only distinct suture is a longitudinal below on either side. . 



In the carapax of the Pagurus punctulatu* (fig. 4 a), the transverse 

 dorsal suture, d, is very distinct and open, being occupied by a cor- 

 neous membrane; it is continued forward along d> , either side to m, 

 and (fig 46) extends to the front margin, at the base of the outer 

 antennae (m) But from d' there is a branch suture passing laterally 

 and downward to n, so as to separate a piece lettered S in the figures; 

 as this suture descends it tees its distinctness, and is not more pro- 

 minent than several other sutures that divide the lateral portions of 

 the carapax in this part into several narrow stripes, that are more or 

 less subdivided by cross sutures. The dorsal suture of the carapax 

 divides it into an anterior (A) and posterior (P) region. In the 

 former, near its middle, there is a U-shaped suture, lettered u u. 

 This suture is distinct and a little open in the punctulatus, and is con- 

 nected posteriorly by a medial suture with the dorsal. 



In the Calcini, the U suture is only faintly indicated, and in the 

 Cenobitse it is not at all apparent. 



In the posterior region of the carapax, the two dorsal longitudinal 

 sutures (p p) are distinct in all the Paguridea, as seen in fig. 4 a. Be- 

 sides these, there is in the punctulatus another longitudinal suture 

 either side, less distinct, marked I in figures 4 a and 4 b. This last is. 

 apparently, the analogue of the longitudinal suture in the Brachyura. 

 In figure 4 b, it is observed, that there is no other lateral suture corre- 

 sponding to the Brachyural. This suture, Z, extends by I" to the 

 angle in the transverse dorsal (d) ; but there is also another continua- 

 tion of it, V, which reaches to d', near the commencement of d' n, and 

 an area, r, is included by these sutures. 



The fact that the suture I is less distinct than p, the dorsal longi- 

 tudinal, shows that the Macroural is beginning to preponderate over 

 the Brachyural structure. In Cenobita, the suture I is wanting, or 

 only appears for a short distance to be lost entirely as it proceeds 

 backward, while the dorsal, p, remains distinct. 



The surface included by the U suture appears to correspond to the 

 medial region in the Brachyura (see page 29), and faint depressions 

 near the eyes appear to mark the anterior limits of this region, corre- 



