CRUSTACEAN LEG SEGMENTS — CARPENTIER & BARLET IO9 



and of their relations with tlie skin fortunately gives us better 

 precision. 



ENDOSTERNITES OF PENAEUS AND ANASPIDES 



We have seen that the postpleural and f ureal formations of the 

 cuticle of Penaeus are wrapped in a common subhypodermal endo- 

 sternal sheath. This endosternite (fig. 6) is unified, that is to say the 

 right and left parts of the scaffolding are medially united by a trans- 

 verse strip (h) going over the nerve cord. Such were the endoster- 

 nites studied in the Lepismatidae, in the prothorax and mesothorax of 

 the Machilidae, etc. On each side of the body, the endosternite is con- 

 nected with the skin by ties. There are three superior arms {so) ; 

 we do not name them with more accuracy because we have not found 

 their homologues — at least their endoskeletal homologues — in the 

 insects. The first arm {so}) is very thin and could be confused with 

 the pleural "tigelle" k of the Apterygota "^ ; but dorsally, instead 

 of being connected with the notum, it is attached to the anterior 

 phragm (fig. 2, ph). The upper arm {sa^) is attached to the posterior 

 phragm ; it is double and each of its branches toward the phragm is 

 enlarged into a blade serving as a support to longitudinal muscles. 

 The arms so} and sa- could respectively correspond to the oblique 

 muscles 75 and yj (prothorax of Lepisma, Barlet, 1951, fig. i) ; sa~ 

 could also correspond to 85 (mesothorax, idem) and 92 (meta thorax, 

 idem). This is one possibility.^* A third and last superior arm 

 (sa^) pertains to the lateral process (fig. 2, x), the morphological value 

 of which we do not know. 



All the other arms of Penaeus have been homologized and are desig- 

 nated therefore, on figure 6, by letters taken over from the notation 

 system which was formerly adopted for the Apterygota. For instance 

 the arm p, the identity of which is obvious ; this arm connects the cen- 

 tral part, g, of the endosternite with the pleural apodeme. The union is 

 direct since there is no pleural process ; in Anwlopenaeus the union is 

 achieved by means of a pleural process. Another lateral arm (r) per- 

 tains distally to the border between the precoxopodite and the coxa. 



23 See Carpentier, 1946, fig. 2 (Ctenolepisma), fig. 5 (Petrobhis) ; Carpentier, 

 1949, fig. 5 (Tomocerus) ; Barlet, 1951, fig. i (Lepisma). 



24 Back in 1927, Cannon (p. 413) examined in a phyllopod crustacean the 

 muscularization of endoskeletal elements. See also Manton, 1928. Without 

 knowing anything about these results, we came to conceive the substitution of 

 "tigelles" for muscles (Barlet, 1946, p. 182; Carpentier, 1949, p. 46, note 7; 

 Carpentier and Barlet, 1951, p. 4). Chadwick (i957) exploited this idea about 

 the Pterygota. 



