THARYBIDAE FROM THE GULF OF MEXICO 



351 



monts, about as long as cpphalothorax. Mandib- 

 ular gnathal lobe (pi. 2, fig. 2) witii moro than 

 half the cutting area comprised of molariform 

 teeth, only dorsalmost 3 teeth setiforni. First 

 maxillae (pi. 2, fig. 8) with endopodite two- 

 segmented, not fused with second basal segment; 

 inner lobe 1 with 12 robust spines; lobe less than 

 half total area of appendage. Second maxillae 

 (pi. 1, fig. 7; pi. 2, fig. 9) with lobe 5 bearing two 

 sensoriform filaments, one seta, and one robust 

 falcate spine; terminal segments with total of 

 approximately 5 sensoriform filaments (exact 

 number could not be determined), each somewhat 

 elongated, exceedingly thin-walled, and flexible; 

 filaments apparently unspecialized at apex. Max- 

 illipeds (pi. 1, fig. 1) with first segment bearing 

 three sensoriform filaments and 2 setae on prox- 

 imal lobe. 



Swimming legs 1^ as figured (pi. 1, figs. 11, 

 13-15); leg 4 approximately twice as long as 

 abdomen (pi. 1, fig. 3). Leg 1 with each segment 

 of exopodite bearing an external spine; spines 

 unequal in length; endopodite with rounded 

 lateral shoulder bearing numerous spiimles. Ex- 

 ternal exopodal spines of legs 2-4 with sagittiform 

 denticles ornamenting upper and lower margins. 



Fifth legs minute, symmetrical, uniramous, two- 

 segmented (pi. 1, fig. 2); basal fusion segment 

 shared by left and right rami; each unisegmental 

 ramus with total of 3 processes, an apical cone 

 bearing spinules along lateral and medial margins, 

 a robust medial spine bearing a ventral row of 

 spinules, and a small lateral spur just proximal to 

 apical cone. 



Adult male: Thorax, cephalic appendages 

 except for first antennae, and swimming legs 

 similar to those in female. First antennae with 

 21 visible segments (pi. 2, fig. 1). .Abdomen with 

 5 segments and furcal rami; second segment long- 

 est, anal segment shortest. 



Fifth legs biramous; first basal segments par- 

 tially fused, second basal segments separate, un- 

 equal in length, left side longer. Right exopodite 

 with first segment elongated, curving mediad; 

 second segment reduced, bearing 1 apical seta. 

 Right endopodite with first segment fused to basal 

 segment, second segment reduced, weakly scler- 

 otized. Left exopodite three-segmented, proximal 

 segment longest; short distal segment bearing 

 terminal and proximal spines, medial face hirsute. 



Left endopodite two-segmented, shorter distal seg- 

 ment scoop-like. 



Types (cf. Localities, Material). — All deposited in 

 United States National Museum. Female holotype, No. 

 99189, selected from material of Alaska, crui.se 4, station 

 11. Paratypes, Nos. 99190-99191. 



Remarks. — The new species can be readily 

 identified by the following combination of charac- 

 ters: the denticulated external spines of the swim- 

 ming legs; the terminal lappets of thoracic fusion 

 segment IV-V, which, in lateral view, are some- 

 what triangular and cover most of the genital 

 segment; the conical apex and medial spine of the 

 female fifth legs; the unusual endopodite of the 

 male right fifth leg, consisting of an elongated 

 process fused to the second basal segment and 

 bearing a reduced apical segment. 



Parundinella manicula, new species 



Plate 2. fig. 12; Pl. 3. Fins. 1-13 



Localities, Material. — Gulf of Me.xico: Lat. 23° 18' X., 

 long. 97° 38' W., (Alaska, cruise 2, .station 11, 7 June 1951, 

 1 m. depth of plankton tow; two adult females). 



Measurements. — Techniques as in preceding species. 



Adclt Female: two specimens, each with similar 

 dimensions; TL 0.81 mm., CAR 3.0:1. 



Diagnosis. — In general resembles P. spino- 

 denticula, differing chiefly in details of rostrum, 

 thoracic fusion segment IV-V, and swimming legs. 



Terminal portion of each side of thoracic fusion 

 segment in lateral view produced in short spini- 

 form process barely overlapping genital segment 

 (pl. 3, fig. 5). Rostrum with filaments longer than 

 basal portion (pl. 2, fig. 12; pl. 3, fig. 7). Second 

 maxillae with terminal segment bearing 6 sensori- 

 form filaments; lobe 5 with 2 such filaments; at 

 least 4 maxillary filaments with flagelliform apex 

 (pl. 3, fig. 4). Leg 1 with shoulder of endopodite 

 conical, bearing encircling row of spinules (pl. 3, 

 fig. 12). Legs 2-4 with external spines of e.xopodite 

 bearing fine hair-like denticles; endopodites of 

 legs 2-3 with moderate number of spinules on 

 posterior face (pl. 3, figs. 9-11). Fifth legs with 

 two segments; basal segment reduced; terminal 

 portion of distal segment with 3 outstretched 

 spiniform processes fringed with hairs; medial 

 margin of distal segment with robust spine 

 bearing ventral row of spinules; face of distal 

 segment ornamented with unevenly distributed 

 spinules (pl. 3, fig. 13). 



Types (cf. Localities). — The two adult females, 

 from which P. manicula is described, were dis- 



