6 THE NAUTILUS. 



city, a mile or more from the French streets. Probably the species, 

 though fully naturalized, has not extended its range so far. 



All the indications are that Rumina was introduced in Mobile a 

 century or more ago, during the French rule, and in all probability 

 it was brought from some French port. The New Orleans race may 

 be as old or older ; both cities date from the 17th century. I shall 

 not be at all surprised if Rumina turns up in Pensacola, another old 

 colony ; and it is more than probable that other European specieg 

 may be found in these Southern cities. 



SPHAEKIIDAE, OLD AND NEW. 



BY V. STERKI. 



A revision, or monograph, of the North American SphceriidcB has 

 been demanded for years. But the way is not |clear : very much is 

 yet to be learned with respect to many species, their interrelations, 

 the extent of their variation, and their distribution. A great deal 

 of material for study from all over the continent is still desirable. 

 A catalogue of the known species, with some notes will be published 

 soon, and on the following pages will be found some descriptions and 



rectifications The numbers cited are those of the special collection 



of Sphceriida. 



Piridium ahditum Haldeman, Proc. Acad. Phila., I. p. 53, 1841 ; 



Prime, Mon. Corb. 1865, p. 68 The P. ahditum muddle has been 



the greatest stumbling block in the otherwise difficult study of 

 Pisidium. Beginning with T. Prime, this " species " has been the 

 general dumping ground into which almost anything was thrown 

 that was not plainly " a black bass or a snapping turtle," or to re- 

 main serious, any Pisidium, even such as noveboracense, variabile, 

 cequilaterale, compressum, etc.. and occasionally Sph. occidentale. 



The authentic specimens, from Lancaster Co., Pa., in the T. 

 Prime collection ^ are of a rather small form but serve to define the 



^They had been there for about seventy years, and remained covered with a 

 ferruginous crust so that their real shape, surface sculpture and color could 

 not be seen. Now they are clean. Of the seven, five are immature, of a rather 

 small form, as noted, 2.8-3.3 mm. long, the others, two pair of valves, are 

 3.8-4 mm. long. The description, in Mon. Corb., is quite inadequate, even 

 with respect to the original form: "very inequilateral" [should be inequi- 



