102 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 48. 



Genus TESSARABRACHION H. J. Hansen, 



Description — Carapace with the frontal plate small, triangular, 

 short and much broader than long (pi. 4, fig. lb); a rostral process 

 is wanting. Eyes very large, higher than broad, distinctly constricted 

 not much above the middle (fig. la). Antennulaa (figs. lb-Id) as in 

 TTiysanoessa; the first joint without distal lobe and very much broader 

 than the two other peduncular joints, which are slender in the female 

 (figs, lb and lc), while in the male the third joint especially is thicker; 

 the upper flagelium depressed and shorter than the lower, which is 

 compressed; both flagella broader in the male than in the female. 

 Antennae as in Ihysanoessa; the peduncle of the endopod elongate 

 (fig. 1/) with its proximal joint more than twice as long as the distal. 



Maxillulse (fig. lg) with the pseudexopod and the palp moderately 

 large. Maxilla (fig. 1^) very broad, both laciniae with the inner mar- 

 gin incised; fourth joint (4) short and somewhat small; exopod (ex) 

 produced along the outer margin of fourth joint and terminating 

 beyond its end. Endopod of the maxillipeds (figs, la and li) with 

 the fourth joint extremely elongate, almost four times as long as 

 the sum of the three distal joints, fifth and sixth joints being very 

 short; the two distal joints are shown in figure lie. 



Thoracic legs (fig. la) about as in TTiysanoessa excepting that both 

 first and second pairs are very elongate, subsimilar; the structure 

 of these legs is in the main like the first pair in a species of TTiy- 

 sanoessa where this pair is very elongate. The three following pairs 

 with the full number of joints in the endopods; sixth pair with the 

 exopod normally developed, while the endopod is in the female (fig. 

 1Z) two-jointed, very slender, and slightly longer than the exopod, 

 but wanting in the male. Seventh pair in both sexes without endo- 

 pod, while the somewhat small exopod is one-jointed, styliform. 



Abdomen as in TTiysanoessa. All luminous organs are present. 



Copulatory organs of first pleopods (fig. lm) so reduced that I 

 suppose that the males seen by me are not adult. The setiferous 

 lobe and the auxiliary lobe with its hooks are well developed, while 

 a median lobe is not marked off from the inner lobe, which has no 

 processes but only two or three fine marginal spines. 



Remarks. — This genus was established by me in 1911 on specimens 

 of a single species found in the material of the United States National 

 Museum. It differs from TTiysanoessa in having no rostral process, 

 while the two anterior pairs of thoracic legs are very elongate and 

 subsimilar; furthermore, the structure of the maxillipeds differs 

 much from that in TTiysanoessa and all other genera. 



