PEREZ FARFANTE: KEY TO AMERICAN PACIFIC SHRIMPS. GENUS Traihyprnratui 



"cebra," or "tigre" shrimp from Central and With the discoveiy of an additional species 



South America will be necessary to establish the of Trachypenaens in the American Pacific, it 



actual distribution of T. faoea as well as that of seems appropriate to present a key to the five 



T. fuscina, both known by the same common members of the genus occurring in the region, 



names. together with the range of each. 



KEY TO THE AMERICAN PACIFIC SPECIES OF Trachypenaeus 



1. Carapace with longitudinal suture short, not extending to hepatic spine. Third ma.xilliped 

 lacking spine on basis; first pereiopod bearing spine on ischium. Thelycum with median 

 plate armed with small anteromedian spine (clearly distinct in juvenile, barely perceptible 

 in adult) ; anterior part of sternite XIV shorter than posterior part, and not produced as 

 paired flaps (Figure 7A). Petasma with dorsal spinelike projection near apex of horn . . 

 T. hrevisuturae Burkenroad 



(From off Punta Arenas, Golfo de California, to El Salvador). 



Carapace with longitudinal suture long, extending posteriorly beyond hepatic spine. Third 

 maxilliped bearing spine on basis; first pereiopod lacking spine on ischium. Thelycum with 

 median plate lacking anteromedian spine; anterior part of sternite XIV longer than poster- 

 ior part, and produced as paired flaps. Petasma without projection near ajjex of horn .... 2 



2. Spine present on posterior end of middorsal carina of last two, three, or four abdominal 

 somites. Telson unarmed. Thelycum with slit between flaps never reaching posterior part 



of sternite XIV, and with median plate short, not reaching gonopores (Figure 7B) 



T. byrdi Burkenroad 



(From Guatemala to Golfo de Guayaquil) 



Spine present only on posterior end of middorsal carina of last abdominal somite. Telson 

 ai'med with lateral spines. Thelycum with slit between flaps reaching posterior part of 

 sternite XIV, if not, with median plate long, reaching, or almost reaching, gonopores . . 3 



3. Rostral teeth 7 to 10, usually 8 or more. Telson with proximal triangular patch of long 

 setae on each side of median sulcus. Thelycum with median ]3late not excavated, short, 

 and protruding ventrally on midportion. Anterior part of sternite XIV lacking platelike 

 base and bearing subrectangular flaps, extending only to posterior part of median plate 

 (Figure 7C) T. similis pacifinis Burkenroad 



(From Bahia Concepcion, Golfo de California, to Tumbes, Peru) 



Rostral teeth 6 or 7. Telson lacking proximal, triangular patches of long setae. Thelycum 

 with median plate strongly excavated. Anterior part of sternite XIV with platelike base, 

 and bearing paired, much elongate, tonguelike flaps, extending well beyond midlength of 

 median plate 4 



4. Telson with posteriormost pair of lateral spines fixed. Thelycum with platelike base of an- 

 terior part of sternite XIV lacking setae on each side, its lateral margins strongly curving 

 posteromesially, forming deep emargination with posterolateral projections (Figure 5A) . . 



T. fuscina sp. n. 



(Golfo de Tehuantepec and Golfo de Guayaquil) 



Telson with posteriormost pair of latei-al spines movable. Thelycum with platelike base of 

 anterior part of sternite XIV setose, its lateral margins almost straight, forming about 



90° angles with posterolateral projections (Figure 5B) T. faoea Loesch and Avila 



(From Guatemala to Golfo de Guayaquil) 



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