her:\ie.ea. 253 



wide as the boclj. Eye spots distinct behind and a little inside of 

 the tentacles. Length, one fourth of an inch ; breadth, one twen- 

 tieth of an inch. 



Found in Charles River and at South Boston Bridge, with E. fns- 

 cata, in July, upon Laoinedea g-eniciilata. 



Well-developed specimens seem quite remote from the last spe- 

 cies on account of size, color, length, and form of papillae, and num- 

 ber of tufts. But they are found in company ; and there are speci- 

 mens of E. fuscata, with only here and there a cluster or a line of 

 dusky dots wliich would lead to tlie suspicion that they might bleiid 

 with each other. 



Family HERM^EID^E. 



Body elongated, not provided with a distinct mantle. Mouth 

 unarmed, or with corneous jaws ; tentacles sometimes wanting ; 

 when present two, dorsal, non-retractile. Gills papillose. Vent 

 usually central, on the posterior half of the back. Genital orifice at 

 the right side. 



The dorsal position of the vent, and the indistinct mantle distin- 

 guish this family from tlie Elysiidcc ; perhaps those genera with 

 horny jaws belong to a distinct family. 



Genus HERilI.EA, Lovi-x. 1844. 



Body elongated, attenuated, without a mantle. Head terminal. 

 Tentacles two, longitudinally folded ; jaws none. Branchiae long, 

 swelled, arranged at the sides of the back. Anus on the body in 

 front of the heart. 



Hermsea cruciata. 



Plate XVII. Fig. 256 

 Hermaia cruciata, Alex. Agassiz, MS. 



Body very slender, the tail much attenuated. Foot narrower than 

 the body, obtusely dilated at the anterior angles. Head small, semi- 

 circular. Mouth inferior. Tentacles dilated and obtusely pointed, 

 the superior face longer than the inferior. Branchise dilated, sliaped 

 much like trefoil or the ace of clubs, the biliary organs within hav- 

 ing a rude cruciate form ; there are seven principal ones on each 

 side and eight or ten intermediate much smaller ones. Length, — ? 



