192 BULLETIN OF THE BUREAU OF FISHERIES. 



the Pandarinae, and the Cecropinae possess such a filament, while it is lacking in the 

 lan-se of the Eun^phorinae. 



The life history ought to count for more than anytMng else when considering 

 relationships, and in all its essential features the life history of the present genus cor- 

 responds with that of the other Lemseans. 



The likenesses, therefore, are as numerous and of greater importance than the 



differences and warrant the retention of this genus LerruBa in the family of the 



Lemseidae. 



G«nus LERN^A Linneeos. 



External generic characters of female. — Head a rounded knob projecting from the anterior margin of 

 the cephalothorax and placed nearly at right angles to the body axis, with a deeply buried, three- 

 parted eye near the center of the dorsal surface. One or two pairs of horns, simple or forked, on the 

 lateral margins of the cephalothorax ; sometimes an impaired horn on the center of the dorsal margin ; 

 horns conical and soft; neck soft, slender, and cylindrical, twristed but not flexed, enlarging gradually 

 into the bodv, which is also cylindrical; a pregenital prominence on the ventral surface in front of the 

 vulvse; on the dorsal surface a bluntly rounded abdomen, which terminates in a minute papilla on either 

 side of the anus ; egg strings elongate-conical or ovoid , eggs large and multiseriate . Two pairs of antennae , 

 second pair uncinate ; a verj' short conical proboscis; mandibles claw-shaped and %vithout teeth ; two pairs 

 of maxillse; four pairs of biramose swimming legs attached to transverse chitin bars, indicating seg- 

 mentation; a fifth pair of one-jointed stumps just in front of the \-ulvae. 



Internal generic characters of female. — (Esophagus short, nearly straight, and diagonal to the body 

 axis; anterior stomach with lateral lobes extending into the bases of the horns and more or less con- 

 voluted; posterior stomach passing insensibly into the intestine, which is straight, the same diameter 

 for its entire length, and is abruptly contracted at the base of the abdomen into a short rectum, which is 

 suspended from the abdomen walls by muscle strands; ovaries paired, close to the dorsal surface and 

 near the posterior end of the body; matured oviducts with two long posterior and two shorter anterior 

 loops; eggs remaining spherical and never flattened anteroposteriorly ; no separate cement glands, the 

 thickened glandular walls of the posterior o\'iducts ser\-ing that purpose; no distinguishable semen 

 receptacles. 



External generic characters of male. — Not developed beyond the fourth copepodid stage, which 

 must hence be regarded as the adult stage ; cephalothorax made up of the head and first thorax segment 

 fused; second, third, and fourth thorax segments free; fifth and genital segments more or less fused; 

 abdomen made up of three segments of about the same size; anal laminae large, each terminated with a 

 very long and stout plumose seta, jointed near its base, and two or three small spines. Appendages 

 similar to those of the female, except that the prehensile claws on the second antermEe and maxillipeds 

 are larger, the rami of the swimming legs are longer and stouter, and there are the rudimeats of a sixth 

 pair at the posterior comers of the genital segment. 



Internal generic characters of male. — OEsophagus long and nearly parallel with the body axis; stomach 

 passing insensibly into the intestine and that into the rectum, the entire tube lined with digestive cells 

 filled with black granules; supra-oesophageal ganglion comparatively small, infraganglion very large 

 and stout and extending back into the genital segment; testes paired but not side by side, in the head 

 and anterior thorax above the stomach and intestine, spindle-sliaped, with the sperm ducts leading 

 from the anterior end back to the large spermatophore receptacles in the genital segment. 



TjTJe of the genus, Lerntea cyprinacea, Linnaeus, first species. 

 (Itemsea, Xipyrt, a lake and town near Argos where Hercules slew the hydra.) 



KEY TO THE SPECIES. 



I. Two cephalothoracic horns, a lateral pair 2. 



I. Three cephalothoracic horns, two paired and lateral, one impaired and dorsal 3. 



I. Four cephalothoracic horns, a dorsal and a ventral pair 5. 



2. Horns directed laterally at right angles to body axis; posterior body not much wider than neck; 

 pregenital prominence inconspicuous (8.40 mm.)". .dia?rac(;/>Aa/a(Cunnington), 1914, p. 194. 

 2. Horns diagonal to bo'dy axis, directed posterolaterally; posterior body suddenly enlarged to 

 four times the diameter of neck; pregenital prominence large (S mm.). 



anomala, new species, p. 104. 



o These figures in parentheses represent the a\-erage length of each species. 



