2 I 2 THE A M ERICA N NA TURA LIST. [Vol. XXXV III. 



has only just begun. The most noticeable feature in this process 

 is the fact that the shell is thin and fragile, so much so 

 that it must be handled very carefully. The second feature is 

 that in the mature animal the shell is not large enough to shelter 

 the whole body in its contracted state. The shell certainly 

 cannot afford particular protection against enemies, but when we 

 remember where the animal lives and its habit of crawling along 

 the mud and sand, we can readily see that it could have no 

 better protection than its color. It imitates the color of the 

 roots of eel grass most closely ; at first sight I have often mis- 

 taken the detached fragments of these roots for Haminea. 



The size of the animal depends largely upon age ; the smallest 

 shell measured was three mm. in width, and five mm. in length ; 

 the average size of the mature shell is 7 mm. in width, and 10 

 mm. in length. The average length of the extended animal 

 including the shell is 2 cm. ; the smallest animal was 8 mm. in 

 length. I can make no definite statement as to the age or size 

 at which H. solitaria begins to lay, but can say that I have 

 never known the smaller ones to lay. In the aquaria the animals 

 die after laying, but I do not believe that this fact can be used 

 as proof that they ahvays do. 



The foot of Haminea possesses, though not clearly distin- 

 guished, the three divisions characteristic of the typical mollus- 

 can foot. From the mesopodium arise the parapodia ; these 

 are lateral lobes, or folds, like extrusions of the edges of the 

 foot. In some of the Opisthobranchia the parapodia (epipodia 

 of Pilsbiy) are highly developed and unite upon the back, com- 

 pletely covering the shell. In our species however the para- 

 podia cover only the anterior part of the shell. 



The young animal moves by stretching forward the head and 

 foot, and then drawing the \isccral mass forward, so that the 

 progress results from an alternate stretching and contraction of 

 the anterior Hexible part of the bod)-. The posterior part being 

 drawn ahead at each contraction. In the mature animals there 



