NO. 1573. PARASITIC COPEPODS— WILSON. 375 



(Dinematura, S15, two, vijjux, tlii-ead, and ovpa, tail, that is a tail 

 made up of two threads, the egg-strings.) 



KEY TO THE SPECIES. 



a. Females, carapace only one-third the entire length and not much wider than the 

 genital segment; rami of the fourth legs and anal larainte long and prominent; 



egg-strings four or five times the length of the body b. 



a. Females, carapace half the entire length or more and much wider than the 

 genital segment; rami of fourth legs and anal laminie short and partly con- 

 cealed ; egg-strings only twice the length of the body or less c. 



a. Males, carapace several times the size of the genital segment; dorsal plates 

 reduced to mere stumps or entirely lacking; rami of fourth legs two-jointed 



and well armed with spines d. 



b. Lobe of sixth segment not projecting beyond the posterior lobes of the geni- 

 tal segment; sixth legs reduced to mere papillje; length 30 mm. or more. . . 



fcrox Kroyer, 1863, p. 377. 



b. Lobe of sixth segment projecting half its length behind the posterior 



lobes of the genital segment; sixth legs as well developed as the fourth; 



length 18 to 20 mm producta Miiller, 1785, p. 380. 



c. Carapace half the entire length or less, not quite twice the width of the genital 



segment; anal laminse l:)roadly foliaceous 



lalifolia Steenstrup and Liitken, 1861, p. 383. 

 c. Carapace two-thirds the entire length and four times as wide as the genital seg- 

 ment; anal laminae narrow oblong hamiltoni Thomson, 1889. 



d. Fourth thorax segment three times as long as wide; abdomen nearly square, 



one-jointed; anal laminae narrow-oblong hamiltoni Thomson, 1889. 



d. Fourth thorax segment considerably wider than long; abdomen oblong and 



two-jointed ; anal laminje as broad as long 



latifolia Steenstrup and Liitken, 1861, p. 383. 



Tliis genus was estabHshed by Latreille in 1829 for the species 

 which Miiller had described as Caligus productus in 1785. Latreille 

 called his new genus Dinemoura, and fortunately gave the etymology 

 of the new word, as so many of his associates have failed to do (see 

 above). Acting upon this, Biu-meister in 1833 changed the spelling 

 of the name to Dinematura which certainly corresponds more correctly 

 to the etymology and was at once adopted universally. 



There was a great amount of confusion in the early descriptions, 

 both in regard to the species and to their hosts, even among such care- 

 ful investigators as Gerstaecker and Steenstrup and Liitken. As late 

 as 1889 Thomson described four species which he referred to this 

 genus; ^hree of them really belong here, but the fourth is as unmistak- 

 ably an Echthrogaleus species. 



The simplest way to rectify this and other similar mistakes is to pre- 

 sent a list of the 18 species which have been ascribed to this genus 

 by the various investigators, with a proper identification for each, so 

 far as this has been rendered possible : 



Dinemoura affinis Milne Edwards, 1840, aliown by Steenstrup and Liitken to belong to 

 their new genus Echthrogaleus, and accordingly becomes Echthrogaleus affinis. 



Dinemoura alata Milne Edwards, 1840, also shown by Steenstrup and Liitken to be a 

 probable species of the genus Echthrogaleus. 



