8 BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



SCOPE AND LIMITATIONS OF THE SURVEY 



This report endeavors to present a convenient handbook of the 

 copepod life of the region that will enable one to identify such 

 species as he may find. For this purpose the descriptions are limited 

 chiefly to distinguishing characters and contain the minimum of 

 technical nomenclature consistent with scientific accuracy. Keys 

 are included as an aid in identification ; the keys to the genera include 

 practically every valid genus thus far described; the keys to the 

 species include only those found in the region. 



The author realizes only too well that the present survey is far 

 from complete and that there must be many species and genera yet 

 awaiting discovery. It is also very evident that in an undertaking 

 like the one here attempted there are many chances of error. It can 

 not be expected that all these have been successfully avoided, but it 

 is hoped that a workable basis has been laid for future study. 



Order COPEPODA 



General characters. — The copepods constitute the largest division 

 of the Crustacea and include free-swimming, benthonic, commensal, 

 semiparasitic, and parasitic forms. They are small in size, often less 

 than half a millimeter in length and very rarely exceeding 10 mm. 

 The body is more or less distinctly segmented, except in a few 

 parasitic genera, and is destitute of a true shell gland. Instead, 

 the cephalon or cephalothorax is often covered with a carapace, and 

 one or more of the thoracic segments may develop paired dorsal 

 plates. The last segment of the abdomen bears a pair of laminae, 

 which may be called anal laminae or caudal rami. The genital aper- 

 tures are on the last thoracic segment, which for this reason is called 

 the genital segment. The two pairs of antennae are well developed 

 and are often used for locomotion or for prehension, the latter use 

 being especially common in parasitic forms. The mandibles usually 

 have a palp, which is often biramose. Fertilization is accomplished 

 by spermatophores, and the eggs are carried, with few exceptions, in 

 external cases attached to the genital segment. There are neither 

 spermatophores nor e^gg cases in the suborder Arguloida, and in the 

 Notodelphyoida the egg cases are replaced by an incubatory pouch 

 on the dorsal surface of the thorax. The swimming; legs are con- 

 fined to the thorax, and the abdomen carries no appendages except 

 the caudal rami. 



Movphological nomenclature. — The body of a copepod is made up 

 of three regions — head, thorax, and abdomen. Wlien one or more 

 of the anterior thoracic segments are fused with the head, the first 

 region is called the cephalothorax. The head is regarded as a single 



