THE SPINY LOBSTER OF SOUTHERN FLORIDA. 295 



The margins of the exopodites are finely scalloped and fringed with short, plumose 

 setae which are provided with nerve fibers, indicating that they are probably sense 

 receptors. 



CARAPACE- 



The carapace of adult males is of different shape from that of adult females. The 

 branchial lobes are highly developed and give this region an oval appearance in contrast 

 to the more cylindrical appearance of the carapace of the female. 



The abdominal somites of the male are progressively narrower posteriorly causing 

 the tail to taper and the uropods to appear proportionately wider than they do in the 

 female, which, however, is merely an optical illusion, since there is no actual difference 

 in width in individuals of the same size. 



THORACIC STERNUM. 



The posterior margin of the sternum of the male (Fig. 270) is narrower than the 

 posterior margin of the female, the last thoracic segment being constricted posteriorly 

 between the greatly developed coxopodites 

 which extend inward, and is raised into 

 small ridges which extend from the articu- 

 lations with the fifth pair of legs toward the 

 center. A small, bilobed part of the sternum 

 lies between the bases of these ridges and 

 extends posteriorly. The sternum of the 

 male is longer than the sternum of the 

 female. , 



The sternum is furrowed by a median -, , „. . , , . .... _ ,. 



J Fig. 269. — Pleopodsof female, spiny lobster. Panuhrus argits. 



groove which extends from between the X 0.7s approximately, a. first pleopod of adult female; b, 



first pair of legs to between the fourth pair. — d e t^^^T^T* M °' 

 A narrow pit lies at the termination of this 



groove, and in the male there are three small tubercles anterior to and in line with the 

 pit. The first of these tubercles is conical and acute and lies somewhat posterior to 

 the bases of the first pair of legs. The second and third tubercles are rounded and 

 but little elevated and lie between the bases of the second and third pairs of legs, 

 respectively. These tubercles seem to form a locking device with those on the sternum 

 of the female. 



The median groove in the sternum of the female (Fig. 271) contains two small 

 tubercles, both of which are conical and lie between the bases of the second and third 

 pairs of legs. The seminal vesicle when present covers the sternum of the female from 

 the third to the fifth pair of legs. The surface of the sternum when the vesicle is 

 removed is striated, these small grooves or striae probably serving to hold the material 

 of the vesicle more firmly in place. 



The posterior margin of the sternum of the female forms a rather broad arch. 

 Small ridges extend from the articulations of the fifth pair of legs toward the center. 

 It is seen when a male and female of the same size are placed with their ventral sur- 

 faces together that the grooves in the sterna form a mold which is nearly filled by the 

 seminal vesicle. The extensions of the coxopodites of the fifth pair of legs of the male 



