6 BULLETIN 152, UNITED STATES NATIONAL MUSEUM 



5. The Xanthidae are by far the most numerous in genera, species, 

 and individuals. Tliey include the large stone crabs, the coral 

 crab of the West Indies, and several of the most important South 

 American forms, but the vast majority are crabs of small or medium 

 size, such as the various mud crabs and coral-reef crabs. 



The Potamonidae or fresh-water crabs will be dealt with in another 

 volume. 



AREOLATE MARKINGS ON THE CARAPACE OF CRABS 



Figure 3 from Dana's "Crustacea, United States Exploring 

 Expedition," part 1, 1852, page 29, is inserted here for convenience 

 of description, especially of Xanthids. The principal parts of the 

 carapace are indicated by letters: F, frontal; M, medial; P, posterior; 

 L, antero-lateral ; R, postero-lateral ; D, E, N, T, S, antero-lateral 

 teeth; d' , s' , smaller, occasional teeth. Subdivisions of the above 

 regions are indicated by a number before the letter. 



Figure 3. — Carapace of a xanthid crab showing the prin- 

 cipal areolations. After Dana 



ANALOGOUS SPECIES ON OPPOSITE SIDES OF THE CONTINENT 



Family PORTUNIDAE 



Atlantic 

 Poriunus (Portunus) gibbesii. 

 Portunus (Achelous) spinimanus. 

 Portunus (Achelous) ordwayi. 

 Portunus (Achelous) spinicarpus. 

 Callinectes sapidus acutidens. 

 Callinectes danae. 

 Callinectes bocourti. 

 Arenaeus cribrarius. 



Pacific 

 Portunus (Portunus) xantusii. 

 Portunus (Achelous) brevimanus. 

 Portunus (Acheloxis) angustus. 

 Portunus (Achelous) iridescens. 

 Callinectes bellicosus. 

 Callinectes arcuatus. 

 Callinectes toxotes. 

 Arenaeus mexicanus. 



Family CANCRIDAE 



Atlantic 



Cancer borealis. 

 Cancer luederioaldti. 



Pacific 

 Cancer edwardsii. 



\ Cancer porteri. 

 \ Cancer plebejus. 



