298 



II are totally absent. The basipodites of the uropods are fused with the 

 endopodites while the exopodites are free. The telson is very small. 



The method of rearing the progeny differs notably from that for 

 other hyperiideans (Pirlot, 1938). The ventral surface of somites I-II of 

 the pereon protrudes strongly and overhangs the deeply depressed ante- 

 rior surface of somite III of the pereon deep into the body. The depression 

 thus formed is protected from the sides by raised ridges, covered with 

 lobes of complex configuration both posteriorly and ventrally, and bifur- 

 cated at the base — by homologues of the oostegites of somites II-III. 

 Thus a firmly closed brood chamber is formed, which is embedded in 

 the abdominal surface of the crustacean, with a narrow protected opening 

 facing posteriorly, which undoubtedly ensures reliable protection of the 

 developing progeny. The oostegites of somite IV are reduced to a small 

 tubercle, but on somite V are modified into a protective valve cover- 

 ing the opening of the oviduct. It has been suggested (Woltereck, 1903) 

 that coincident with the above-described structure of the brood chamber 

 and its remoteness from the efferent ducts of the reproductive system, 

 specialization occurred in the distal part of pereopods VII in the mature 

 female as an adaptation for the transfer of eggs from the opening of the 

 oviduct to the brood chamber. 



Early stages of development of the crustaceans exhibit significant 

 morphological differences from the late stages and adults; they were 

 earlier named physosoma (Woltereck, 1903) or thaumonectes (Senna, 

 1903). They are characterized by spherical building of the thoracic por- 

 tion, relatively small head, and strong ornamentation of the body surface 

 with spines. 



The family includes one genus represented by several species, living 

 mainly at levels deeper than 1,000 m. 



1. Genus Cystisoma Gu6rin-M6neville, 1842 



Guerin-Meneville, 1842: 214; Stebbing, 1888: 1318; Barnard, 1916: 286; 

 1932: 268; Pirlot, 1938: 364; 1939: 33; Bowman and Gruner, 

 1973: 26. — Thaumops Willemoes-Suhm, 1873: 206. — ^Thaumatops 

 Martens, 1875: 189. 

 245 Length of females up to 140 mm, of males, on average, up to 50 mm. 



The head in females is spherically bulged, its height considerably 

 exceeding the height of the person. In males the head is of the same 

 height as somite I of the pereon; dorsally it is convex and from the base 

 of antennae I straightly truncated toward the oral appendages (frontoven- 

 tral surface), antennae I have an indistinct border between the base and 

 the flagellum; in adults they may be longer or shorter than the head, 

 sometimes with highly developed apical glands. The head, in addition to 

 lateral marginal denticles, ventrally bears a number of structures in the 



