106 PROCEEDINGS OP THE NATIONAL MUSEUM. voi,. 53. 



But Pennatula was the name of a genus of alcyonaiian coral 

 polj'^ps, which gradually came into general use, and which is still 

 retained in the group of sea fans known as Pennatulacea, with the 

 type genus Pennatula. 



Hence Oken, on establishing the new species diodontis in 181G, 

 suggested Pennella as a new name for the genus and it has been 

 universally adopted. 



Thus although Linnaeus antedated Oken by many years we can 

 not use his name for this copepod genus, but must adopt the one 

 given by Oken. 



External generic characters of female. — Cephalothorax globular, 

 hemispherical, or semielliptical, usually somewhat flattened dorso- 

 ventrally and often with the anterior end squarely truncated and 

 covered with short and tumid processes; the rounded posterior end 

 gives off two or three cylindrical chitin horns, unbranched. Neck 

 very long, cylindrical, and comparatively wide, increasing gradually 

 in diameter and passing insensibly into the trunk. The latter is 

 cylindrical, often transversely ridged, and straight; abdomen long 

 and tapering to a bilobed tip, Avith a pair of tiny anal laminae armed 

 with long setae; a row of appendages along either side of the 

 abdomen, nearer the ventral surface, and branched so as to resemble 

 the barbs and barbnles of a feather. Egg strings from once to several 

 times the length of the body, straight and filiform; eggs numerous 

 and uniseriate. Antennae persisting in the mature adult while the 

 two pairs of maxillae apparently disappear; first two pairs of legs 

 close together, third and fourth pairs removed a short distance. 



Internal generic characters of female. — Bilateral symmetry com- 

 pletely preserved ; mouth tube on the anterior end of the head or on 

 the ventral surface near the anterior margin ; proboscis with a meager 

 supply of muscles; esophagus inclined to head axis and supported 

 by a rigid chitin framework suspended from the ventral wall of the 

 head; stomach without convolutions or lobes; intestine straight, 

 nearer the dorsal surface, and considerably narrowed in the abdo- 

 men; rectum short and straight. 



Ovaries two-thirds the length of the trunk, tapered posteriorly, 

 the ends distinct, the central portion more or less completely fused; 

 oviducts with a short loop where they leave the anterior ends of the 

 ovaries, and comparatively narrow ; cement glands extending the en- 

 tire length of the trunk, the ducts the same length and diameter as 

 the glandular portion. 



Chitinogen layer of body wall forming an opaque network of pig- 

 mented fibers over the inner surface of the thick chitin skin. 



Genus habitat. — This genus burrows from apparently any locality 

 on the outer body surface of its host through the skin and tissues. 



