6 INVERTEBRATA OF MASSACHUSETTS. 



form of elongated papillae, arranged in rows along the sides or 

 on the back. 



Mr. Couthouy ventures the conjecture, that these papillae are 

 not the real respiratory organs, because he has seen that the ani- 

 mal will voluntarily throw them off, from slight causes, or that 

 it may be forcibly deprived of them without material injury ; 

 which, he justly remarks, would not be hkely to be the case, were 

 they organs of so much importance as the branchiae. He is dis- 

 posed to regard them as merely subsidiary to the function of res- 

 piration. He has described and figured the following species. 



EoLis Bostoniensis. Bost. Journ. JVat. Hist., ii. 67, pi. 1, 

 f. 1. Body an inch or more in length, foot large, tapering to a 

 point behind, color faint brownish-white ; tentacula four, cylin- 

 drical, rather long ; branchiae numerous, purplish-brown tipped 

 with white, disposed in four or five clusters of 12 or 15 filaments 

 each, on each side. 



This is probably E. rufibranchidlis, Johnston, Mag. JS\tt. 

 Hist., v. 428, f. 85, and Jlnnah of JVat. Hist., i. 121. He 

 states the number of clusters in his species to be variable, and 

 more or less definite, and that the color varies, being reddish- 

 brown, rose-color, scarlet, &c. 



EoLis salmonacea, Couthouy. Bost. Journ. J\^at. Hist., ii. 

 68, pi. 1, f. 2. Body oblong-ovate, an inch or more in length, pale 

 straw-color ; tentacula four, rather short and blunt, the upper 

 ones minutely serrated at the sides ; branchial filaments about 100, 

 flattened at their sides, disposed in lines along the back, of a 

 beautiful salmon-color. 



EoLis diversa, Couthouy. Bost. Journ. JVat. Hist., ii. 187, 

 pi. 4, f. 14. Size and shape about the same as the preceding ; 

 color a pale yellow, tinted red ; lower tentacula long and slender, 

 upper ones short, smooth, rounded, somewhat behind the first ; 

 branchial appendages about 90, slender, color orange, disposed in 

 double rows along the back, with intermediate shorter ones. 



Differs from the last in the form and position of the tentacula, 

 the color of the branchiae, &c. ; but it may possibly prove the 

 same. 



