166 



the last whorl, and narrowest part of it close to the aperture, or the 

 penult whorl. 



With, then, the one species from Polynesia, Electrina succinea, 

 the total of Stoastomidce amount to 81 species known ; and I proceed 

 to propose an entirely new arrangement of them. Professor Adams 

 foresaw the necessity and propriety of it. In his ' Monograph of 

 Stoastoma,' p. 4, occur the following passages : — "The value of this 

 genus is equal to that of the Lamarckian genera of Cyclostoma and 

 Helicina. If these should he generally received as families, sub- 

 divided into several genera according to the plan of Dr. L. Pfeiffer, it 

 will be entitled to constitute a distinct family, Stoastomidce. Some 

 of the characters rarely, if ever, occur in other genera, while the 

 specific differences consist partly in slight modifications of these 

 characters. Such are the blunt but not reflected edge of the labrum 

 and the spiral lamella issuing from the umbilicus. The geniis has 

 thus a very obvious type, quite distinct from any hitherto discovered. 

 An affinity with the Cyclostomidce is established between Apero- 

 stoma (Troschel) and the depressed and discoidal species of Stoa- 

 stotna." " Its affinity with the Helicinidce is established between 

 Lucidella (Swainson) (??), and some of the conical species, as S. 

 Redfieldianum and S. Leanum, by their general form and sculpture, 

 and by the form of the base. But observations on the animals will 

 be of more value on this subject. We were not so fortunate as to 

 obtain living specimens. While preparing this Monograph, a cor- 

 respondent informs us that S. pisum when alive is sea-green." 



In raising Stoastoma into a family, I am thus justified by Pro- 

 fessor Adams, and only carry out his views in calling it, Family 

 Stoastomidce, Adams. 



Fortunately I happen to be " the correspondent " who found the 

 shell S. pisum in " a living state ;" when it is, and continues after, 

 if so taken, of a " sea-green " colour externally. I have also exa- 

 mined the outward form of the animal. The following are my rough 

 original notes made long ago upon it : — 



"Stoastoma pisum. 



" The animal seems to have but one pair of horns, and is thus 

 shaped. 



[The drawing supposes the animal to be in motion.] 



