REPORT ON THE COPEPODA. 37 



I refer these specimens, only provisionally, to the genus Calanus, from which they 

 differ in some important particulars, — in the structure of the maxilla-palp, and in the 

 presence of only three segments in the female abdomen. But as the male is unknown, 

 and as the structure of the maxilke in allied species has scarcely as yet received 

 sufficient attention, it seems best, for the present, to defer any attempt to frame a 

 complete generic definition. 



Eucalanus, Dana. 



Eucalanus and Calanus (in part) Dana, Crust, U. S. Expl. Exped. (1852.) 

 Calanus, Lubbock, Trans. Entom. Soc. (1856.) 

 Calanella, Claus, Die frei lebend. Copep. (1863.) 



Body straight, slender and elongated ; anterior portion of the head much attenuated 

 and elongated ; forehead triangular, prominent, rostrum very slender and furcate. Last 

 four thoracic segments very small. Anterior antennae composed of twenty-three or 

 twenty-four joints, bearing (in the male) numerous club-shaped appendages ; setae small, 

 except towards the apex. Inner branch of the posterior antennae seven or eight-jointed, 

 shorter than the outer branch. Mandible palp composed of one large and one very small 

 two-jointed secondary branch. Anterior foot-jaws of moderate size, posterior excessively 

 long. Four pairs of feet in the female, five in the male, the fifth pair one branched and 

 prehensile. Eyes small, simple. Abdomen short, composed of four joints in the male, of 

 three in the female. 



The anterior portion of the body, composed of the head and first thoracic somite, is 

 extremely long, — more than twice the length of the rest of the body (PI. VI. fig. 1) ; 

 the forehead, from which springs the rostrum, forms a triangular projection between the 

 two rounded, somewhat bulbous sides, behind which there is a slightly constricted neck 

 (fig. 2). The animal, though large, seems to be excessively fragde, at any rate in its 

 antennae and feet, the antennae especially being often broken away so as to leave 

 visible only a very small portion of their original length. The smaller branch of 

 the posterior antenna? (fig. 4) is fusiform, eight-jointed, the first two joints being 

 large, the last six small and gradually tapering towards the apex ; the larger branch 

 is two-jointed, large, and bears long terminal setae. The mandibles (fig. 5) are broad 

 and numerously toothed at the apex, the basal joint of the palp very large, the apical 

 portion much smaller, and composed of four joints ; to the basal joint is attached 

 a very small two-jointed branch, which bears three apical setae. The maxillae (PI. II. 

 fig. 8) are very large, and their distal segments are more than usually elongated. The 

 anterior foot-jaws (PI. VI. fig. 6) have the normal form, but according to Claus, are 

 more powerfully armed in the female than in the male, the lateral segments unusually 

 large. The posterior foot-jaws are very large, in the female six-jointed (PI. II. fig. 9), 

 elongated, and not differing much from the normal form ; in the male (PI. VI. fig. 7) 



