6 CRUSTACEA OF ALABAMA. 



are Calanus, Eucalanus, Rhincalanus, Heterochaeta, Leuckartia, Undina, Scolecithrix, 

 Euchaeta, Calanoides, Aetidius, Drepanopus, Phyllopus, Temora, Temorella, Centro- 

 pages, Candace, Acartia, Pseudodiaptomus, Diaptomus, Limnocalanus, Osphranticum, 

 Epischura, Heterocope, Corynura, Calanopia, Pontellopsis, Parapontella, Pontella, 

 Anomalocera. 



GENUS CALANUS, Leach. 



Cetochilus, Claus, Etc., 



Cephalothorax slender, six-jointed, cervical suture generally present, antennae 25- 

 jointed, slender, alike in both sexes, except that in the male there are club-shaped append- 

 ages to the segments; posterior maxilliped elongate, composed of two thickened and 

 lobed basal and five setose terminal joints ; feet, five pairs, similar, bi-ramose, each ramus 

 three-jointed ; abdomen in the male five-, in the female four-jointed. The species of this 

 genus are among the more slender of the family, the antennae especially being elongated 

 and graceful. 



Calanus americanus, s P- n ( ? ) 



(Cf. C. LONGIREMIS, Claus.) 



(Plate I, Fig. 9.) 



Our knowledge of this species is insufficient to permit a satisfactory description. 

 In most points which can be compared with the meagre description of G. longiremis, 

 there is close agreement. The body is very slender and the joints of the antennae are 

 very narrow, reaching beyond the caudal setae. The head is marked by a slight cervical 

 suture. The abdomen has but three obvious segments in the female, probably the faint 

 line of union between the third and fourth was overlooked. First abdominal segment 

 very prominent anteriorly in the female, spinulous above ; caudal stylets rather long for 

 the genus, median seta greatly enlongated, exceeding entire abdomen. The anten- 

 nae bear long spines upon the apical and antipenult joints ; antennules with the apical 

 segment of two-jointed branch, 10-setose, median portion of inner ramus 8-articulate, 

 terminal segment with three setae ; anterior maxilliped with extremely long thorny setae 

 on the apical segment, three median lobes, each with two strong setae, basal lobe with 

 four; second maxilliped with two lower segments elongate, the basal with three setose 

 lobes, second segment with five setae, five lobes of terminal portion rather short, with 

 small setae ; both branches of the five pairs of feet three-jointed, terminal spine long, ser- 

 rate, and curved. 



The above description may serve to identify an animal certainly abundant in the 

 Gulf and among the most beautiul and graceful of the Copepoda. None of the species 

 hitherto found in the Atlantic seem to at all agree with the present form. 



