CALANOID COPEPODS FROM GULF OF MEXICO 



361 



in one or two rows of lon<; spinules, and tlie medial 

 niarfrin l)ears sliort latenii spiniiles. In all of the 

 available paraconcinna males the apex of this 

 segment bears a row of closely spaced fine hairs and 

 the anterodistal corner is ornamented with five- 

 six subequal serrations; the lateral margin is fur- 

 nished with short hairs. 



The male of E. plana Mori is also somewhat 

 similar to the new species. From Mori's (1937) 



description, plana is distinguished from paracon- 

 cinna by the absence of Ri and presence of large 

 spinules lx)rdering Re-j on the left fifth leg, and by 

 the acute angle formed by the rostrum and the 

 frontal organ. 



I wish to thank Dr. Philip St. John (Brandeis 

 University) for furnishing me with the records 

 and specimens of the new species obtained by the 

 Atlantic from the Cape Hatteras region. 



Family STEPHIDAE 



STEPHOS Scott 



Stephos deichmannae, new species 



Plate 3, figs. 1-15 



Localities, Mutcriul.—GuU of Mexico: lat. 23°18' N., 

 long. 97°37' W. {Alaska, cruise 2, station 11, 7 June 1951, 

 1 ni. (leptli of plankton tow) ; lat. 29°06' N., long. 9.3°0O' W. 

 (Alaska, crui.se S, station 2, 12 February ID.'ni, 6 m. depth 

 of ijlankton tow ) . Material consisting of 22 adult females, 

 4 adult males, numerous immature copepodites ; juveniles 

 taken onl.v at cruise 2, station 11. 



Mea.si/femenfx. — Specimens measured from 

 right lateral view at 100 X, magnification; length 

 of cephalothorax from imaginary line between 

 anteriormost limit of forehead to posterodorsal 

 margin of intersegmental membrane between 

 thoracic fusion segment IV-V and genital seg- 

 ment ; length of abdomen from anterodorsal mar- 

 gin of genital segment to posteriormost limit of 

 right furcal ramus. Otherwise, methods are as 

 presented under the first species described above. 



1. Adult fem.\le: 22 sijecimens, TL range 0.62-0.73 

 mm., mean with standard error <).68±.0O6 uim., standard 

 deviation 0.030 mm., CAR range 2.9-3..5 :1, mean 3.2:1. 



2. Adult male: Four specimens: TL 0.61 mm., CAR 

 2.7 :1 ; TL 0.66 mm., CAR 2.7 :1 ; TL 0.66 mm., CAR 2.4 :1 ; 

 TL 0.62 mm., CAR 2.8 ;1. 



Diagnosis. — A relatively small species somewhat 

 resembling S. scotti Sars, S. fuU&ni Scott and 

 Scott, and S. gyrans (Giesbrecht). 



Adult female : Differs from above species in 

 details of thoracic fusion segment IV-V, genital 

 segment, and fifth legs. 



Terminal portions of thoracic fusion segment 

 IV-V asymmetrical, in dorsal view left side ex- 

 tending more posteriad; in lateral view right side 

 somewhat truncate and lacking spiniform process 



(fig. 3), left side extending posteroventrad in 

 lobiform process (figs. 4, 7). 



Genital segment in dorsal view with asymmetri- 

 cal lateral swellings, swelling of left side larger, 

 right side bearing one lateral spine (figs. 1, 7) ; 

 occasionally two lateral spines present. Posterior 

 margin of genital orifice with elongated spine, 

 differing from that in gyrans and fixJtoni; spine 

 relatively straight, midventral, and extending 

 posteriad to approximate midlength of following 

 segment (figs. 1, 3). 



Fiftli legs similar in form to those of gyrans, 

 difi'ering in spinal ornamentation; second segment 

 with distal border bearing horizontal row of 

 spinules; terminal segment with horizontal row 

 of styliform spinules at approximate midlength, 

 row of scalelike spinides on distal lialf of lateral 

 margin, and fine hairs on medial margin (figs. 

 5,9). 



Tiip<s icf. Localities). — All deposited in United States 

 National Museum. Female holotype: No. 991S6; selected 

 from material of Alaska, cruise S, station 2. Paratypes ; 

 No. 99187 {Alaska, cruise 8. station 2) : No. 9918S (Alaska. 

 cruise 2, station 11). 



Further description. — Cephalon and tlioracic 

 segment I separated by weak suture as in gyrans. 

 Ri of leg 1 with robust hemispherical shoulder 

 bearing one spimde (fig. 13). Legs 2-4 with ex- 

 ternal spines of Re bearing minute serrations on 

 distal Iwrder (figs. 10-12). Ijeg 4 approximately 

 one-third longer than abdomen (fig. 3). First 

 antennae in female about as long as combined 

 lengths of cephalothorax and genital segment ; 

 antennal segments 1-2 partially fused, 8-9 com- 

 pletely fused. First antennae in male barely as 

 long as cephalothorax. Cephalic appendages 



