FISHERY BULLETIN': VOL. 69, NO. 3 



penaeiis byrdi Burkenroad the telson lacks 

 spines. The telson of the members of the genus, 

 thus, must now be more broadly characterized 

 as having several pairs of lateral movable spines, 

 or several pairs of movable spines anteriorly and 

 a fixed posterior pair, or unarmed. Furthermore, 

 the evidence presented here indicates that the 

 character of the posteriormost pair of telsonic 

 spines is not a unique character of the series 

 Parape7iae2is. 



The branchial formula of Trachypenaeus was 

 given by Dall (19.57) as follows: pleurobranch- 

 iae on somites IX to XII; a rudimentary arthro- 

 branchia on somite VII, anterior and posterior 

 arthrobranchiae on VIII to XII, and a posterior 

 arthrobranchia only on XIII; mastigobranchiae 

 (ejnpodites) on VII, VIII and XII [first, second 

 maxillipeds and third pereiopod] , sometimes also 

 on X and XI [first and second pereiopods] . All 

 American species possess this combination of 

 branchiae, including epipodites on the first and 

 second pereiopods, and, in addition, a vestigial 

 anterior arthrobranchia on somite XIII. 



In Trachypenaeus. the anterior arthrobranch- 

 ia on somite VIII is considerably disiilaced dor- 

 sally, and appears to occupy the position of a 

 pleurobranchia; however, its attachment is on 

 the arthrodial membrane. In Figure 1 the open- 

 ings of the branchiae on somites VIII and IX, 

 together with the proximal parts of the second 

 and third maxillipeds, are depicted ; this figure 

 clearly shows that the two arthrobranchiae on 

 somite VIII are attached to the arthrodial mem- 

 brane, like those on somite IX, whereas the 

 pieurobi'anchia on the latter somite has its origin 

 on the pleural membrane. 



Burkenroad (1934a; see also 1934b) divided 

 the genus Trachypenaeus into two subgenera, 

 Trachypenaeus and Trachysahtmbria, the latter 

 possessing epipodites on the first and second 

 pereiopods, and a thelycum with a median pocket 

 on sternite XIV; the former lacks these char- 

 acters. Later, Burkenroad (19.59) observed that 

 some members of Trachysalambria lack such 

 epipodites and, thus, questioned the "usefulness" 

 of his division. Recently, a number of species 

 from the Indo-Pacific have been described which 

 bear ejnpodites on the first two i)airs of i)ereio- 

 pods but the thelyca, as indicated by Racek and 



Dall (1965) , difi'er fi'om that Burkenroad attrib- 

 uted to the members of Trachysalambria. Con- 

 sequently, more investigations are needed to in- 

 terpret the interrelationships of the species of 

 the genus. It should be i)ointed out, however, 

 that all American species of Trachypenaeus ex- 

 hibit the characters given by Burkenroad for 

 T rachysalamb ria. 



Figure 1. — Trachypenaens fi(sciiia sp. n., 9 3.3 mm car- 

 apace length, off Barra de San Marcos, Chiapas, Mexico. 

 Dorsal view of proximal part of second and third maxilli- 

 peds and attachments of gills on arthrodial and pleural 

 membranes of somites VIII and IX (second maxilliped 

 has been displaced laterally), a. Podobranchia. b, b'. 

 Anterior arthrobranchiae. c, c'. Posterior arthrobran- 

 chiae. d. Pleurobranchia. 



The spelling of the generic name used here, 

 Trachypcymeus instead of Trachypcnen.H as was 

 originally iniblished, is based on the decision 

 reached by the International Commission on Zoo- 

 logical Nomenclature, Opinion 864, 1969, Bull. 

 Zool. Nomencl. Vol. 25, Parts 4-5, \^. 138-147. 



636 



