64 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 53. 



LERNAEENICUS AFFIXUS, new apecles. 



Plate 6, figs. 48-Gl. 



Host and record of specimens. — The tomcod, Microgadus tomcod^ 

 seems to be the most frequent host of this species, and the United 

 States National Museum collection contains the following series of 

 specimens obtained at Woods Hole, Massachusetts. A single female 

 to serve as the type of the new species, Cat. No. 47792 ; a dozen fe- 

 males, Cat. No. 12311 ; 8 entire tomcod heads, with about 50 parasites 

 attached, Cat. No. 47797; 8 tomcod heads, with 100 parasites at- 

 tached, Cat. No. 47798 ; 40 females from the same host, at Fire Island 

 Beach, Long Island, Cat. No. 35982 ; 8 females, Cat. No. 47794. 



It has also been found upon a few other hosts — three vials, contain- 

 ing 2, 3, and 8 specimens, respectively, from the killifish, Fundulus 

 heieroclitus, with Cat. Nos. 47793, 47795, and 47796 ; a single female 

 from the white perch, Morone amencana, Cat. No. 12301 ; two females 

 from the glut herring, Pomolohus aestivalis^ Cat. No. 42296. 



Specific characters of female. — General body form very similar to 

 radiatus, with the three regions as distinctly separated; head turned 

 ventrally at right angles to the thorax, cylindrical, slightly larger 

 at the base and tip than in the center. No horns on the head, but a 

 single pair, short and unbranched, on the sides of the thorax oppo- 

 site the fourth legs; occasionally these horns may be branched, and 

 rarely there is a second pair posterior to the first, which are reduced 

 to mere stumps. 



This species attaches itself to a bone, and hence the horns are not 

 used for anchorage. The organ of fixation is on the anterior end of 

 the head, just in front of the second antennae, and is made up of two 

 lamellae on either side, whose bases are attached along the midline 

 of the front of the head. At their bases these lamellae lie flat upon 

 the surface of the head and point away from each other ; they then 

 gradually curve forward until their tips are parallel, thus assuming 

 the shape of half a cylinder. 



The anterior surface of the lamellae or the inside of the half 

 cylinder is applied directly to the bone, and cements itself so firmly 

 to the latter that the two can be separated only by cutting, the long 

 axis of the bone being parallel with the body axis of the copepod. 



The edges of the lamallae are often thickened to make the fasten- 

 ing more secure. The thorax, genital segment, and abdomen are like 

 those of radiatus, except that the trunk is relatively lonj2jer and 

 wider, being from 10 to 15 times the diameter of the neck. The egg 

 strings are about one-third the diameter of the trunk and a little 

 longer, and are usually fairly straight. First antennae short and 

 stout, two-jointed, with two small spines on the terminal joint; sec- 



