210 THE AMERICAN NATURALIST. [Vor. XXXIV. 
FAMILY I. TANAID&. 
a. Pleopoda only three pairs. Uropoda simple, short, single-branched. 
Tanais Audouin and Edwards 
a’, Pleopoda five pairs. Uropoda double-branched. 
6. Eyes wanting. 
c. Inner branch of uropoda two to three-jointed. Pleopoda in 
female very small or rudimentary. 
d. Incubatory pouch formed only by two lamelle issuing 
from bases of fourth pair of legs. Pleopoda in 
female rudimentary. Gnathopods alike in both-sexes. 
Mandibles well oie with cutting edge coarsely 
dentated. . . . Cryptocope G. O. Sars 
d'. Incubatory pouch bona: Pleopoda in female small, 
sometimes wanting. Gnathopods in female of nor- 
mal appearance, hand dilated, fingers strong, thumb 
serrulated, in male slender, fingers simple. Man- 
dibles very small and feeble in structure, with cutting 
edge narrow eptognathia G. O. Sars 
c. Inner branch of seine: eight to nine-jointed. Pleopoda 
well developed. . . Aloatanais Norman and Stebbing 
&. Eyes present. 
c. Gnathopods in male imperfectly chelate, without any finger, 
or with finger very short and immovable 
Heterotanais G. O. Sars 
c. Gnathopods in male with chelz fully developed. 
d. Gnathopods in male sometimes very much elongated, 
with carpus attenuated, hand very large, oblong, 
finger elongate and curved, immovable, strongly 
tuberculate within. Thoracic appendages not spe- 
cialized into an anterior and a posterior series. 
Marsupium of female formed of eight large lamella 
from the four first free segments. 
Leptochelia Dana 
@. Gnathopods in male with chelz very stout, the distal 
section of the penultimate joint extremely broad, with 
a toothed margin. "Thoracic appendages specialized 
into an anterior and a posterior series. Marsupium - 
of the female of the normal structure. 
Neotanais Beddard 
Genus Tanais Audouin and Edwards. 
a. Periopoda having the first three joints short and broad, dilated and 
affixed to the sides of the thorax like plates of mail. 
Tanais loricatus Spence Bate, A, 10 fms. 
a’, Periopoda, with joints not dilated, slender. 
