densities differ greatly over its range. It is scarce 

 on the northern coast of Cuba and rare on the 

 southern coast, except in Oriente province, where 

 I collected many specimens in the bays of Guanta- 

 namo and Santiago de Cuba. It is not common in 

 the rest of the Greater Antilles, the Virgin Islands, 

 and the Lesser Antilles. P. a. subtilis is moderately 

 abundant in some areas along the coast of Central 

 America. 



Croker (1967) did not cite this subspecies as 

 constituting part of the commercial catches in the 

 northeast coast of South America, but collections 

 from that region identified by Holthuis (1959), 

 Bullis and Thompson ( 1959a, b) , and me show that 

 P. a. subfilk is not only present, but is apparently 

 rather abundant in the area. Curiously enough, 

 whereas Croker reported P. d. nofialk as present 

 in the commercial catches, Holthuis recorded but 

 a smgle female of P. d. notialis from Surinam, and 

 Bullis and Thompson did not find it along the 

 northeast coast of South America. P. a. suhtilis 

 abounds along the southernmost part of its range. 



P. a. suhtilis has a rather wide bathymetric 

 range; it has been caught in waters as deep as 105 

 fm., NE. of Punta de Gallinas, Departamento de la 

 Guajira, Colombia {Oregon Sta. 5684, lat. 12°30' 

 N., long. 71°48' W.), at 100 fm., west of Cabo de la 

 Vela, Colombia {Oregon Sta. 4913, lat. 12°09' N., 

 long. 72°47' W.), and at 95 fm. off Punta de Gal- 

 linas, Departamento de la Guajira, Colombia 

 {Oregon Sta. 5685, lat. 12°29' N., long. 71°54' W.) , 

 the type locality. 



The population of P. a. suhtilis from the Gulf 

 of Paria to the neigliborhood of Camocim, Brazil, 

 as discussed by Perez Farfante (1967), is distin- 

 guishable from the populations at both ends of the 

 range of the subspecies. In the Paria-Camocim 

 population, the adrostral sulci are shorter (fig. 59) 

 (ending % to V^ of the length of the carapace 

 from its posterior margin), shallower and acumi- 

 nate posteriorly, and the rostrum is longer and 

 more sinuous. Many individuals, however, show 

 feeble indications of the posterior portion of longer 

 adrostral sulci as well as isolated pits where these 

 sulci would seem to liave terminated. In addition, 

 at both ends of the range of this intermediate 

 population, in the Gulf of Paria, and near Camo- 

 cim, individuals witli tlie al)0\e cliaracters were 

 found intermingled with individuals possessing 

 the character typical of the slirimp found to the 

 north and south. Also, in Colombia and Vene- 

 zuela, the ranges of variations of the leiisith and 



width of the adrostral sulci and the length of the 

 rostrum overlap those of specimens from the Gulf 

 of Paria to northeastern Brazil; figure 59 shows 

 the overlapping in length of adrostral sulci. Fur- 

 thennore, the ratio K/S is not significantly differ- 

 ent throughout the range : in the sample* from the 

 Caribbean region and eastern Brazil the ratio K/S 

 is modally 3 and in those from the Gulf of Paria- 

 Camocim, 3.5. In the Caribbean and eastern Brazil 

 areas, K/S ranges from 2 to 5 and at Gulf of 

 Paria-Camocim K/S ranges from 2 to 8, but in 

 only a small percentage of the samples does the 

 K/S reach values above 5. It appears as if the 

 observed differences could be due to environmental 

 conditions, because the intermediate population 

 occupies the area receiving the discharge of the 

 Orinoco and Amazon Rivers. 



Relationships 



P. a. subtilis differs from all the other grooved 

 Pcnaeus in the western Atlantic by the narrower, 

 shorter, and peculiarly shaped posterior portion of 

 the adrostral sulci and (except from P. paulensis) 

 by the shallower, usually internipted, and shorter 

 median sulcus. It may also te distinguislied from 

 typical P. a. aztecus by the K/S ratio, which is 

 modally 3.5 (dorsolateral sulcus narrow), whereas 

 in P. a. aztecus it is 1.25. Also, females of P. a. 

 subtilis tend to have the anterior and posterior 

 processes wider and often the anterior process flat 

 instead of deeply concave. In both subspecies the 

 third pereopod has about the same lengths for each 

 carapace length to 40 mm. c.l. ; in larger individuals 

 of P. a. aztecus it is longer (compare figures 29 and 

 38, which show the lengths of the carpus — indica- 

 tive of the lengths of the third pereopod — for 

 various carapace lengths in P. a. aztecus and P. a. 

 suhtilis. respectively). The third jsereopod of P. a. 

 subtilis less than 40 mm. c.l. appears shorter than 

 that of P. a. aztecus for, at most, it exceeds the 

 antennular peduncle by only the length of the 

 dactyl, whereas in P. a. aztecus it exceeds the 

 peduncle by the entire length of the propodus. This 

 apparent difference in length is due to the shorter 

 antemiular peduncle in P. a-, aztecus. 



P. a. xuhtil/s may be distinguished from its close 

 relative P. paulensis (which has a similar ill-de- 

 fined median sulcus) by the broader doi-solateral 

 sulcus with a rounded dorsal lip and by the sinu- 

 ous rather than straight rostnun. Moreover, in 

 P. a. suhtilis males the ventral costa of the petasma 

 has a different sluiiie, and its attached border is 



552 



U.S. FISH AND WILDLIFE SERVICE 



