42 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 53. 



them. The mouth being on the ventral surface of the first segment of 

 the part posterior to this apparent neck shows that it is not a neck 

 at all and that the swollen anterior end of it is not a head. But in 

 spite of such an anomalous arrangement this genus admirably sup- 

 plements the others in the family. In most of the genera {Lernaeo- 

 cera, Pennella) the excessive elongation of the body of the adult fe- 

 male takes i^lace in the fifth and genital segments, the first four 

 thorax segments having no sliare in it. In Peniculus the third and 

 fourth segments are elongated a little but not nearly as much as the 

 fifth and sixth segments. In Lernaea all the thorax segments share 

 in the elongation, the posterior ones more than the anterior. And 

 here in Therodamas also all the thorax segments share in the elon- 

 gation, but the anterior ones are elongated more than the posterior, 

 and the head, which in other genera has only sent out lateral and 

 dorsal processes, is here elongated anteriorly. The wide separation 

 of the swimming legs and the multiseriate, sack-like egg strings place 

 the genus in the subfamily of the Lernaeinae. 



Lernaeenicinae, new subfamily. 



Svhfamihj characters of female. — Cephalothorax armed with hard 

 chitin horns, more or less profusely branched, or with soft cushion- 

 like lateral processes, or with branched frontal processes, sometimes 

 two of these combined; neck cylindrical and usually very slender 

 and chitinous; trunk straight, without a sigmoid curve; genital seg- 

 ment enlarged but destitute of a pregenital prominence ; 2g^ strings 

 long and thread-like; neither in coils nor spirals, eggs uniseriate. 

 Two pairs of antennae, the second pair chelate; mandibles in the form 

 of straight spines; one or two pairs of maxillae; no maxillipeds; first 

 two pairs of swimming legs close together just behind the head, ons 

 or tAvo other pairs at short intervals. 



Suhfamily characters of male {genus Sarcotretes) . — Body like 

 that of Cyclops., composed of a cephalothorax covered with a cara- 

 pace and furnished anteriorly with a stout attachment filament; 

 three free thorax segments, and a fused, one-jointed, genital seg- 

 ment and abdomen; anal laminae rather small, each armed with four 

 or five tiny setae of varying length. Antennae and mouth parts 

 like those of the female with the addition of the rudiments of a pair 

 of maxillipeds; two pairs of biramose swimming legs with two- 

 jointed rami, a third pair uniramose, rami also tAvo-jointed. 



Parasites of salt-water fish exclusively. 



Ontogeny of genus Sarcotretes. — The genital protoplasm in the 

 posterior end of the ovary gradually forms into egg mother-cells 

 and these into egg daughter-cells, which are uniformly distributed 

 throughout the anterior half of the ovary without forming filaments. 



