THE 



AMERICAN 

 JOURNAL OF SCIENCE, &c. 



Art. I. — Description of a Crustaceous Animal, belonging to the 

 genus Caligus — C. Americanus ; by Charles Pickering, M. D. 

 and James D. Dana, Members of the Yale Natural History So- 

 ciety. 



Read before the Yale Nat. Hist. Soc, Feb. 20, 1838. 



The species of the genus Caligus, and of other aUied genera, 

 are commonly called fish-lice, in allusion to their parasitic mode 

 of life. The individuals which are the subject of the following 

 remarks, infest the Common Cod* of this part of the American 

 coast. 



During the fall of the year, when the shoal fish are brought to 

 the New York market,! the Caligi are exceedingly abundant. Oc- 

 casionally, forty or more individuals may be taken from a single 

 fish. As the season advances, the fish are taken in fewer num- 

 bers off Sandy Hook and Long Island, and afford a much smaller 

 proportion of parasites. The Caligi are most numerous on the half- 

 grown fish ; they are found indiscriminately on the head or different 

 parts of the body, but never within the gill-covers, A European 

 species has been said to live under the scales : we have never ob- 

 served this peculiarity in the species on this coast ; indeed, the 

 closeness of the small scales of the cod, renders it impossible. 



* It has not been satisfactorily ascertained whether the cod of this coast is iden- 

 tical with the European species, Morrhua vulgaris ; this, however, is the common 

 opinion. 



t These investigations were made at the city of New York, and occupied the 

 latter part of November last, together with the following months, December and 

 January. 



Vol. XXXIV.— No. 2. 29 



