364 THE GENUS CALLINECTES—M. J. BATHBUX. vol.xviii. 



Carapace very large, coarselj^ grauulate; areolatioiis very i)romineut. 

 Cardiac regiou distinctly divided into two lobes by a median furrow. 

 Intramedial area narrow, its length greater than its posterior width. 

 Front (Plate XXIV, fig. 9) slightly upturned, with four broad rounded 

 lobes, the inner pair the smaller and less advanced, and more <leeply sep- 

 arated from each other than from the lateral. Submedian tooth small; 

 in the males about as much produced as the outer frontal teeth; in the 

 single female at hand, it is less advanced than the front. Suborbital 

 teeth obtuse. The anterolateral teeth are triangular, with a short 

 closed fissure between their bases; margins denticulate. The second, 

 third and fourth teeth are almost equilateral and acute; the fifth to the 

 eighth inclusive are acuminate, with successively longer tips, which in 

 the seventh and eighth curve forward. The lateral spine is from two 

 and one-third to nearly three times the length of the preceding tooth. 

 Sternum flat. The penultimate segment of the abdomen of the male 

 (Plate XXV, tig. J>) is constricted in its proximal half, but not so much 

 so as in C. sapidus and C. bocoiirti. The appendages (Plate XXVI, fig. 

 9) reach almost to the extremitj^ of the terminal segment and are more 

 strongly curved than in C. sai)idus or C. hoeoiirti. Abdomen of female 

 (Plate XXVIl, fig. 8) similar to that of G. hocourti, but the penultimate 

 segment is shorter. The spines on the anterior or inner margin of the 

 merus are strdngly curved. Spines of the manus long-pointed. The 

 costte are very coarsely tuberculate. 



Size. — This is the largest species known, attaining a width of 7^ or 8 

 inches. The largest specimen examined is from Cape St. Lucas, and is 

 in the Museum of Comparative Zoology. Length to sinus, 83 mm.; to 

 tip of frontal teeth, 8G; width, 191; length of lateral spine, 21; of pre- 

 ceding tooth, 7.3. This specimen is like old specimens of C. sapidus in 

 having the lateral teeth narrower, sharper, and with more concave mar- 

 gins than in younger specimens. The median frontal teeth are also 

 more slender. The frontal teeth are so much worn that their real rela- 

 tive lengths can not be seen; but in all other specimens the median are 

 not so advanced as the lateral, the difference being greater in the 

 smaller specimens. 



The only young specimens are three, a male and two females, which 

 were without label in the Mexican exhibit at the AVorld's Columbian 

 Exposition. They have the branchial regions very much swollen, and 

 the posterior margins of the anterolateral teeth are longer than the 

 anterior. They approach no other known speeies. 



The localities from which specimens have been examined are as 

 follows: 



Cape St. Lucas (type locality) : John Xautus, 2 large males, 1 ovigerous female 

 (Mus. Comp. Zool.); oue dried fragmentary specimen (No. 2413, U. S. N. M.), 

 having the carapace marked in 8timpsou's handwriting, " C. diacanthus, Cape 

 St. Lucas, Xantus," and bearing no other hibel. 



Acapulco, Mexico (No. 18507, U. S. N. M. ). A large number were collected by the 

 Hassler Exj)edition, and are in the Museum of Comparative Zoology. They 

 are all adult, the smallest being 108 mm. wide. 



