THE CANCROID CRABS OF AxMERICA 5 



In the same lists there have been entered, besides specimens in the 

 National Museum, many types examined elsewhere, as well as such 

 specimens from other collections as increase our know^ledge of the 

 range of the species, but for lack of space no attempt has been made 

 to record all of the many specimens examined in museum and 

 private collections. 



In the color notes made by Doctoi Schmitt on Tortugas specimens 

 the 1886 edition of Ridgway's "Nomenclature of Colors" is used. 



THE CANCROID OR CYCLOMETOPOUS CRABS OF AMERICA 



The term "Cancroid or Cyclometopous " is used in contrast to 

 "Grapsoid or Catometopous." Together they form the Brachy- 

 rhyncha of Borradaile.^ 



1. In general, the carapace of the Cancroids is broader than 

 long. At the outset we find an exception to the rule in the family 

 formerly known as Corystidae but latterly, in obedience to the 

 International Rules of Nomenclature, as Euryalidae. They have 

 affinities with the anomuran crabs and have not only elongate cara- 

 paces but long, coarse antennae and a rather prominent front 

 (between the orbits), which is more than one can say of most of the 

 group. The buccal cavity narrows forward while the outer pair 

 of maxillipeds reach forward almost to the antennules. A small 

 family, especially in our hemisphere, where it is restricted to South 

 America. 



2. The Portunidae or swimming crabs can with few exceptions 

 be distinguished by then- hind legs which are broad and fiat, adapted 

 for swimming. The carapace is of good width with teeth or spines 

 on the margins. A large family, including the so-called "blue 

 crab," the chief edible crab of the Atlantic coast of North America, 

 formerly very abundant, now rapidly becoming a luxury. 



3. The famil}^ Atelecyclidae is limited in species and distribution. 

 The carapace is narrow, often approaching the circular, oblong or 

 pentagonal. Typically the movable part of the antennae is well 

 developed but it may on the other hand be absent or rudimentary, 

 giving rise to a series of curious forms peculiar to South America. 



4. The Cancridae are represented in America by the genus Cancer, 

 recognized by its broad oval carapace, and numerous side teeth. 

 The species are numerous and many of them attain a large size 

 and include several of economic value, especially on the west coast 

 of North America. 



! Ann. Mag. Nat. Hist., ser. 7, vol. 19, 1007, p. 466. 



