ECONOMIC RELATIONS, ANATOMY, AND LIFE HISTORY OF GENUS LERN^A. I93 



3. Lateral horns simple, dorsal one bifid at apex; pregenital prominence inconspicuous; abdomen short 



(lomm.) dolabrodes, new species, p. 194. 



3. Lateral and dorsal horns all dichotomously branched 4- 



3. Lateral horns three or four pronged; dorsal horn stout and bifid at apex; pregenital prominence large; 



body club-shaped; abdomen long and wide (7.50 mm.) pectoralis (Kellicott), 1882, p. 195. 



4. Lateral horns once bifid, dorsal horn twice bifid; body spindle-shaped; pregenital prominence 



absent (8 mm.) lagenula (Heller), 1865, p. 195. 



4. AH three horns twice bifid; body club-shaped; pregenital prominence divided, its two lobes 



and the abdomen the same size (10 mm.) catoslomi (Kr0ycr), 1863, p. 195- 



4. Lateral horns twice bifid; dorsal horn simple or once bifid; body club-shaped; pregenital 

 prominence simple and much smaller than abdomen (12 mm.). .Zor/wo (Kellicott), 1882, p. 193. 



S- Dorsal and ventral horns about the same size 6. 



5. Ventral horns much smaller than the dorsal 9- 



6. Pregenital prominence simple and much shorter than abdomen 7- 



6. Pregenital prominence divided , its lobes nearly as long as the abdomen 8. 



7. Abdomen short and pliunp; pregenital prominence forming a distinct heel; ventral horns bifid 



(5.75 mm.) phoxinacea{Kx(l,y&r), 1863, p. 195. 



7. Abdomen short and plump; pregenital prominence not forming distinct heel; dorsal horns bifid 



(13.50 mm.) esocina (Burmeister), 1835, p. 195. 



7. Abdomen long and stout; pregenital prominence forming distinct heel; all the horns simple 



(14 mm.) haplocephala (Cunnington), 1914, p. 195. 



8. Pregenital prominence divided into three broadly rounded lobes; horns long, slender, and 



straight (13.50 mm.) pomotidis (Kr0yer), 1863, p. 196. 



8. Pregenital prominence twice bifid, forming four narrow lobes; horns short, plump, and curved 



(10 mm.) cruciaia (Le Sueur), 1824, p. 196. 



9. Pregenital prominence divided into distinct lobes; dorsal horns simple and undivided 10. 



9. Pregenital prominence simple or only slightly indented; dorsal horns distinctly forked 11. 



10. Abdomen a short and broad triangle; dorsal horns cylindrical and standing out laterally at 



right angles to body axis (9 mm.) tenuis (Wilson), 1916, p. 196. 



10. Abdomen long and conical; dorsal horns flattened dorsoventrally and curved forward in 



front of head, parallel to body axis (11.50 mm.) variabilis (Wilson), 1916, p. 196. 



II. Abdomen short and inclined to body axis; egg cases broadly elliptical; ventral horns mere knobs 



(14 mm.) barnimii (Hartmann), 1870, p. 196. 



II. Abdomen short and inclined to body axis; egg cases narrow and elongate; ventral horns half the 



length of dorsal (22.50 mm.) cyprinacca (Linnaeus), 1758, p. 196. 



II. Abdomen long and parallel with body axis; ventral horns very short and slender (10 mm) 

 iemnocephala (Cunnington), 1914, p. 196. 



Remarks. — Dr. W. A. Cvmnington recently (1914) issued a valuable little paper on " Parasitic 

 Eucopepods from Tanganyika, Africa," in which he included a list of described species with synonyms 

 and a key to all the known species (seven in number), including three new ones described in the 

 paper. But he overlooked Hartmann 's paper (1870) on barnimii, one of the best that has ever been 

 published, and also Kellicott's two papers describing iortua and pectoralis. The key published by 

 Cunnington is an excellent one and is made the basis of the one here presented. One or two facts in 

 connection with it are worthy of comment. It is based entirely upon characters that can be seen with 

 an ordinary hand lens, as such a key ought to be for convenience. Amongst these characters the horns, 

 of course, take a prominent place, but too much specific value ought not to be placed upon either the 

 number or the arrangement of the horns. Consequently all the other external characters, including 

 the average length of the species, have been introduced into the key, and these should be given their 

 full value. 



Cunnington, in writing of his own key, said: "I am not responsible for the rather remarkable 

 assertion that L. catostomi possesses three cephalic arms, which, of course, renders the head quite 

 asymmetrical" (p. 823). 



The author can not see how the possession of three horns is any more remarkable than the 

 possession of two or four. And certainly a median, dorsal, unpaired horn no more destroys the sym- 

 metry of the head than does the nose or the mouth on a man's face compared with his two eyes or ears. 

 Moreover, there are five species which have such a dorsal horn instead of one, as will be seen from 

 the key. 



