NO. 1222. ISOPODS OF THE ATLANTIC COAST— RICHAIW/SON. 525 



Fuinily IX. CYMOTHOID.E. 



ANALYTICAL KEY TO THE GENERA OF CYMOTIIOID.E.^ 



a. Head not at all iinmersetl or wet in the first thoracic segment. 



h. Uropoda and terminal negment ciliated. Eyes large, conspicuou.s. .25. .Egathoa. 

 h'. Uropoda and terminal segment not ciliated. Eyes small. 

 0. Posterior angles of first segment of body prominent or produced, very often 

 acute; posterior angles of the following segments increasing gradually 

 in length, the first of these very often .scarcely prominent, tlie posterior 

 ones very often produced, abruptly longer than the first. Epimera of 

 the first segments extending beyond the posterior angles of the seg- 

 ment; posterior ones produced, acute 26. Nerodla. 



cf. Posterior angles of first six segments of body scarcely or not at all promi- 

 nent, those of seventh segment produced. Epimera of first segments 

 very often almost or (juite reaching, or not reaching by a short dis- 

 tance, the posterior angle of the segment. 

 d. Body compact. Head not constricted at base. Uropoda very often more or 

 less longer than terminal segment. Legs gradually increasing in length. 



27. A^iilocra. 



d'. Body relaxed. Head constricted at the base. Uropoda much shorter than 



terminal segment. Legs gradually and much longer successively; 



seventh pair abruptly very much so 28. Olencira. 



a' . Head more or less immersed or set in first thoracic segment. 

 h. First pair of antennae contiguous at the base. 

 c. Epimera of the first pair with a carina produced in the form of a spoon in 

 female. Ungulpe very long, unequal in length; those of the third pair 

 longest, abruptly longer than second pair. Terminal segment trans- 

 verse 29. Ceratothoa. 



6-'. Epimera of the first pair not produced in female. Ungute mostly very short, 

 very rarely long, equal in length. Terminal segment subtriangular, 



semicircular, often bilobed 30. Memertia. 



h'. First pair of antennie manifestly distant at the base. 

 0. Abdomen manifestly separated from the thorax, abruptly narrower than 



thorax 31. Cymothoa. 



(f. Abdomen continuous with thorax, not narrower than thorax. 



d. Body hunched or compressed 32. Agarna. 



d' . Body evenly convex, not hunched, 

 t'. Abdomen very little or scarcely immersed. Segments of thorax either 

 equal in length or the first segment abruptly longer and the last segment 



abruptly shorter than the others 33. lAvoneca. 



ef. Abdomen very deeply and profoundly immersed. First segment of the 

 thorax manifestly longer than the second; six posterior segments gradu- 

 ally decreasing a little in length 34. Irona. 



2S. >EGATHOA Dana. 



ANALYTICAL KEY TO THE SPECIES OF iEGATHOA. 



a. Frontal margin of head produc-ed anteriorly in a median linguate projection. 



69. JEgathoa Ibvjnifrons, new species. 



a'. Frontal margin of head not produced anteriorly in a median projection. 



b. Surface of head smooth, evenly convex. Second pair of antenna? ten-jointed. 



First thoracic segment longer than any of the succeeding segments, which 



are of equal length 70. Mgaihoa loligmca Harger. 



^The definitions of genera are taken from Schioedte and Meinert's Monograph of 

 the Cymothoida?, Naturhist. Tidssk., XIII, XIV, 1881-1884. 



