mo. 1766. 8TALK-EVED CRUSTACEA OF PERT] A' 177//// V. 537 



and the orbit; surface uneven, granulate, two transverse granulated 

 ridges. Front and orbits together equaling one-third width of cara- 

 pace; front between orbits four-toothed, teeth broadly rounded; 

 orbits and'eyes large. Chelipeds long and strong; arm with four 

 large spines on inner edge and a terminal spine on outer edge; palm 

 prismatic, with seven granulate ridges and a spine at either end; 

 fingers as long as palm; prehensile edges armed with stout irregular 

 teeth. Legs flattened, last pair very broad, especially the last two 

 segments, which form a swimming paddle. Abdomen of male broad 

 at base, narrow distally; third to fifth segments fused; terminal 

 segment in both sexes longer than one-half of penult segment; 

 appendages of first segment in male sinuous, reaching nearly to end 

 of abdomen. 



Width IS to 19 em. 



Taken with casting net, mouth of river Tumbes, January 15, 1908. "Jaiva." 

 Said to be very abundant at times. ( >nly a few were seen during my stay in the region 

 (January 15 to February 15). Of economic value. 



Not previously reported from Peru. 



Distribution. — From Cape St. Lucas, Lower California, to Peru. 



CALLINECTES ARCUATUS Ordway. 



Plate 56. 



Callinectes arcuatus Ordway, Boston Journ. Nat. Hist., vol. 7, 1863, p. 578. — 

 Rathbun, Proe. U. S. Nat. Mus., vol. 18, 1896, p. 362, pis. 20; 23, fig. 1; 24, 

 fig. 8; 25, fig. 7; 26, fig. 7; 27, fig. 7. 



Similar to the preceding, but smaller; intramedial area shorter and 

 broader; antero-lateral region smoother; frontal teeth more triangu- 

 lar, acute, the middle pair very small. Terminal segment of abdo- 

 men in both sexes shorter than one-half of penult segment; append- 

 ages of first segment in male straight or nearly so, not reaching ter- 

 minal segment of abdomen. 



Width 10 to 12 em. 



Oyster beds of Matapalo, near Capon, February 3 ("Jaivas"). 



On the beach at Las Vacas, near Capon, January 2:',, L908 ("Jaiva"). 



Not previously known from Peru. 

 Distribution. — From Lower California to Peru." 



ARENiEUS MEXICANUS (Gerstaecker). 



Plate 37, fig. 2. 



Eurtcnotn nn.riciina ( i kiist.kckkh, Arch, fur Naturg., vol. 22, pt. I, L856, p. L31, 



pi. 5, figs. 3 and 4. 

 Neptunus mexicanus A. Milne Edwards, Crust. Reg. Mex., 1879, p. 212, pi. 42, 



fig. 3. 



Of medium size. Carapace twice as broad as long, hexagonal, 

 with the antero-lateral margins more arcuate than in Callinectes and 



o Professor Porter records a fragment of a Callinectes from Coquimbo, Chil 



