CYMOTHOIDEA. 757 



and Ceratothoa, the three posterior are much shorter than the others, 

 while in Nerocila, the three posterior are much longer than the others. 

 Again, in the three preceding genera none of the thoracic segments 

 nor their epimerals are acute behind, while in Nerocila, the posterior, 

 at least, in all the species, are acute, and sometimes the anterior. The 

 spiniform pieces below the abdominal segments distinguish the species 

 from the AnilocraB, to which they are otherwise related. 



Nerocila lata. 



Corpus latius, vix sesqui longius quam latum. Thorax non ohlongus 

 segmentis 3 posticis latere acute productis. Epimerw thoracis total 

 acuta?, breves, fttw basin Imarum attingentes. Abdomen non oblongum, 

 segmentis 5 anticis lateraliter productis, tenuibus, ultimo scutiformi, 

 multo angustiore quam quintum, non oblongo, basi paulo latiore, 

 extremitate late rotundatd et medio subangulatd. Appendices caudales 

 aculeatxB, acutce, externa longiore, paulo curvatd. 



Body broad ; length about one and a half times its breadth. Thorax 

 not oblong, armed with acute points on sides of last three segments. 

 Epimerals of thorax all acute, short ; sixth reaching base of seventh. 

 Abdomen shorter than broad ; five anterior segments laterally long- 

 produced and slender, the last scutiform, not oblong, little broader 

 at base, widely rounded at apex, a low angle at middle of posterior 

 margin. Caudal appendages aculeate, both acute; the exterior 

 longer and a little curved. 



Plate 50, fig. 6 a, animal, natural size ; b, same, more enlarged, 

 ventral view; c, first antenna; d, second antenna, right side; d', 

 same, left side. 



Rio Janeiro. 



Length, one inch ; greatest breadth, two-thirds of an inch. Colour 

 bluish-slate, little clouded with a darker or brownish shade. Head 

 small, posterior angles nearly acute, about as long as broad. Thorax 

 not longer than greatest breadth. Epimerals all aculeate, increasing 



190 



