Bull. U. S. B. F., 1909. 



Plath XLIII. 





f/O' 



Fig. 



^(^;-.:' 



^(".yj 



Fig. 3. 



Fig. I —Oblique section through large claw of lobster in first larval stage, showing open tendon pocket {t p) of adductor muscle; 

 before fusion of flattened cuticular walls has taken place. 



Figs. 2 and 3. — Jaws of cracker claw of lobster weighing about 12 pounds, disarticulated and placed to show correspondence of 

 ''molars when jaws are closed. Proximal and distal tubercles of index {p. d) alternate with larger "crushers" of thumb 

 kP^. d^); h{s), socket, and h{b), ball, of terminal hinge joint; up. and /. ser, upper and lower series of altematelj- displaced pro- 

 tective spines of propodus. 



Fig. 4. — Profile of seminal receptacle of female, from molted shell. A, anterior; D, dorsal; St. xin, modified sternum of somite 

 xiii; bar, sternal bar, supporting seminal sac, x with dotted line marks plane of section of seminal sac shown in figure 3, plate 

 xuv; s, proximal socket of first joint of fourth pereiopod. 



Fig. 5. — Skeleton of first abdominal somite of male Irom behind, showing stylets directed forward and meeting uii mid-line, their 

 probable position for conveyance of spenmatophore to seminal receptacle in impregnation. A, anterior, and p, posterior 

 margin of somite; b, posterior ball of hinge joint; /, tergum; ep, epimeron;*/, sternum; pi, reduced pleuron, which forms "but- 

 ton ' ' to carapace. 



Fig. 6.-^Seminal receptacle shown in profile in figure 4, as seen from under side, presenting median elastic lips of pouch into 

 which nibs of stylets are supposed to be pressed in copulation. Figures 4-6, nearly natural size. 



