18 THE NAUTILUS. 



to the writer by Dr. Wni. H. Dall, have furnished preparations of 

 the teeth enabling us to fix the the generic positions of these inter- 

 esting little species. P. pugetensis proves to be a Zonitid, with the 

 dentition much like that of Pseudohyalina mtiniscula and milium, 

 perfect laterals 4, as in mitni&i-tilu, while milium has 2 or 3. The 

 jaw, imperfect in my preparation, looks like that of minusciila. 



P. randolphii has the characteristic dentition of Puiietum, and 

 with pi/ijma-um (v. minutissimuni) and conspeetum it makes three 

 species of this genus for America. There are two in Europe, pyg- 

 mceum Drap. and massoti Bgt., and one in Africa, cryophilum Mar- 

 tens. Some other minute Patuloids will doubtless prove to belong 

 to Punciwn when their dentition is examined. P. randolphii has a 

 narrower umbilicus than our other species. 



So ambiguous are the shell characters of these genera of small 

 Zoiiitiiiir and EndodontidcR that, as the event has proved, Dall was 

 fully justified in the liberal use of question-marks in his provisional 

 generic references. The moment their soft parts come under the 

 microscope, broad distinctions between the groups appear, leaving 

 no uncertainty as to the limits of the genera and families. The 

 difficulty is to get the animals of these liliputian races alive or suit- 

 ably preserved for dissection. 



The classification of the numerous groups and genera of Zo>iifi<!n 

 is still in an embryo condition. The forms with well-developed 

 spiral shell inhabiting North America fall into groups as follows: 

 a. 9 System bearing a long dart-sack surmounted by one or more 

 coronal glands, and usually containing a slender, curved 

 dart. Subfamily ARIOPHANTIN.E Pils. 



b. Caudal mucus pore present ; shell without opaque color- 

 markings, Genus GASTRODONTA. 

 c. Shell with internal teeth or a layer of callus on the floor 



of last whorl, s.-g. 



cc. No internal teeth or callus. 



d. Surface polished, s.-g. 



</il. Surface conspicuously striate or costulate, 



s.-g. Pseudohyalina. 



bb. No caudal pore ; shell with streak, band or flame markings, 



Genus PcEClLOZONlTES. 

 aa. 9 System lacking dart-sack, etc. 



Subfamily ZONITIN.E Pils. 



