132 THE AMERICAN NATURALIST. [Vor. XXXIV. 
paddle. They include the widespread pelagic Portunus sayi, 
the “lady crab," or “calico crab” (Ovalipes ocellatus), and the 
edible Callinectes. 
In the key which follows, the same terms are employed to 
indicate geographical distribution as in Professor Kingsley's 
keys to the Macrura, with two additions. Although the species 
of the southern half of Florida are excluded from the key as 
belonging properly to the West Indian fauna, those of the 
remainder of the Gulf coast are included. It has also seemed 
advisable to indicate by the letters CH those species whose 
northern limit is Cape Hatteras. The characters used are as 
follows : 
4 Alaska south. 
P Puget Sound to San Francisco. 
D Monterey to San Diego. 
W Atlantic coast south to Cape Cod. 
M Cape Cod to North Carolina. 
S South Carolina to Florida. 
G Gulf of Mexico. 
CH Cape Hatteras, northern limit. 
The bathymetrical limit is 100 fathoms. 
KEY TO THE FAMILIES OF THE TRIBE CYCLOMETOPA. 
A 
Antennulæ folded longitudinally. Outer maxillipeds long, overlapping 
the epistome . CANCRIDÆ Latreille, Alcock 
A’, Antennule folded idineversely or ‘ obliquely transversely. Outer maxil- 
lipeds usually not overlapping the epistome. 
B. Last pair of legs not modified for swimming 
PILUMNIDÆ Leach = XANTHID# Alcock 
B’. Last pair of legs usually modified for swimming, with the last two 
joints compressed, very broad and paddle-like. Carapace widest 
at the last antero-lateral marginal spine. Usually from 5 to 9 
antero-lateral spines or teeth . . . PoRTUNID# Leach, Miers 
KEY TO THE GENERA OF THE FAMILY CANCRIDA. 
4. Buccal cavity completely closed by the outer maxillipeds . . Cancer 
A’, Buccal cavity not completely closed by the outer maxillipe 
B. Carapace broader than long, pentagonal. . nae Telmessus 
B. Carapace longer than broad, suboval . . . . . Erimacrus 
a 
