USNM, Rio Pantepec, Tuxpan, AprU 10, 1963, 

 S. Basulto and M. C. Rodriguez de la Cruz. 

 2 9, USNM, Rio Pantepec, TiLxpan, February 11, 

 1964, members Sociedad Cooperativa Rio Pan- 

 tepec. 3 cf 5 9, INIBP-USNM, mouth of Rio 

 Pantepec, Tuxpan, June 7, 1964, C. Tovar and 

 R. Marquez. 6 cf 4 9, INIBP-USNM, Laguna 

 La Tapada, November 28, 1963, A. Macias and 

 U. Barron. 1 c^, INIBP, Laguna de Buen Pais, 

 12 km. W. of Alvarado, F. Lachica and 

 F. Carmona, April 1965. 



Tabasco: 5 cf 5 9, INIBP-USNM, Laguna 

 Pajonal, July 4, 1963, D. Fuentes. 



Campeche: 2 9, INIBP-USNM, Golfo de 

 Campeche, 26 fm., April 30, 1959, R. Ramirez 

 and M. Flores. 5 cJ' 3 9, INIBP-USNM, Boca 

 Nueva, Los Pinos, April 28, 1959, R. Ramirez 

 and M. Flores. 3 c? 1 9, INIBP-USNM, N. of 

 Isla del Carmen, 3 fm., May 5, 1959, R. Ramirez 

 and M. Flores. 



Diagnosis 

 Adrostral carina and sulcus short, ending at 

 epigastric tooth. Petasma ^\-ith inner surface of 

 distal portion of lateral lobe \\-ith diagonal ridge 

 and prominent fold near rounded distoventral 

 corner; emargination median to inner lappet 

 shallow. Thelycum with pair of anterolateral, 

 sharp ridges, posterior portions of which bend 

 mesially, and pair of posterior, fleshy, closely set 

 lobes on sternite XIV ; posterior margin of sternite 

 XII bearing pair of relatively small scalloplike 

 projections. 



Description 



ROSTRUM (flg. 4) 



Teetli , mode —^(percentage distribution: 



8/2—70, 9/2—12, 7/2—13, 8/3—1.50, 9/3—1.25, 



8/1—0.75, 10/2—0.50, 6/2—0.50, 7/0—0.25, 4/1— 



0.25 ; N = 400) + epigastric; ventral teeth relatively 



far apart, first tooth usually opposite or anterior 



to last dorsal tooth; rostrum slender and long, in 



juveniles extending to base of distal one-fifth of 



thickened portion of lateral antennular flagelkun; 



maximum length in relation to c.l. (carapace 



r 1 

 length) obtained at 10 to 16 nun. c.l. (ratio -V 



(rostrum length) as high as 1.10) ; decreasing pi-o- 

 gressively with increasing length of shrimp, reach- 

 ing midlength of second antennular segment in 



shrimp 50 mm. c.l. (ratio -^^ reduced to about 



c.l. 

 0.55) ; rostrimi straight, slightly concave postero- 



ventrally ; highest portion of blade usually at level 

 of second, occasionally of third doi-sal tooth, and 

 at level of first tooth in some young; third dorsal 

 tooth level with anterior margin of carapace ; tip 

 slender and long, almost one-half of length of 

 rostrum. Postrostral carina narrow and relatively 

 short., ending Vs to 1/13 c.l. from ix>sterior margin 

 of carapace, shorter in larger individuals. Median 

 sulcus shallow, interrupted and variable in shape : 

 consisting of anterior elongated concavity in wider 

 portion of postrostral carma, either blunt or con- 

 tinumg as line toward ej^igastric tooth, and 

 leading jwsteriorly by a groove to a narrower con- 

 cavity; sometimes both concavities separated by 

 constriction, and often median sulcus consisting of 

 a single blimt anterior concavity; median sulcus 

 represented posteriorly by few minute pits. In 

 small specimens median sulcus consisting of three 

 or four pits. Adrostral carina rounded and short, 

 ending at level of epigastric tooth. Adrostral sul- 

 cus shallow and short, same length as adrostral 

 carina. 



CARAPACE (fig. 5) 



Ijength in proportion to total length smaller in 

 juveniles; according to my data increasing sud- 

 denly at subadult stage. Gastrofrontal sulcus 

 absent ; gastrofrontal carina absent except for a 

 short, almost imperceptible rib present sometimes 

 at level of first two dorsal teeth. Orbito-anteimal 

 sulcus wide anteriorly, narrowing posteriorly to 

 below apex of hepatic spine, there widening into 

 base of spine. Gastro-orbital carina pronounced, 

 sharp, and relati^■ely short, occupying posterior 

 % to % distance between postorbital margin and 

 hepatic si3ine. Cervical sulcus short and shallow 

 extending dorsally to two-fifths c.l. from postor- 

 bital margin of carapace; in small individuals 

 extending farther posteriorly as line. Hepatic 

 carina % to 14 c.l., sharp, sloping anteroventrally 

 to end 1/1 8 to y^z c.l- from anterior margin of cara- 

 pace ; hepatic sulcus shallow. Antennal spine acute 

 and relatively short; hepatic spine prominent. 



ANTENNULES 



Lateral flagellum long, seven-tenths to almost 

 same length as antennular peduncle, slightly 

 longer and witli articles shorter than median 

 flagellum. Median flagellum exhibiting sexual 

 dimorphism : in adult males markedly flattened 

 dorsoventrally, with two closely set rows of stout 

 processes of unecpial sizes along midportion of 



I 



472 



U.S. FISH AND WILDLIFE SERVICE 



