182 THE CHICAGO ACADEMY OF SCIENCES. 



the vaginal opening, the two organs forming the short vagina; albu- 

 miniparous gland large, oval, very tightly bound down to the oviduct; 

 first accessory albuminiparous gland very large, embracing the oviduct ; 

 second accessory albuminiparous gland small, round, attached to the 

 oviduct a very short distance above the first albuminiparous gland. 



The organs are colored as follows : Albuminiparous gland bright 

 yellow, prostate black shading into dirty white, oviduct yellowish or 

 dirty white, receptaculum seminis flesh-colored on its lower part, bright 

 orange on its upper part; penis-sac yellowish; the other organs white. 



The measurements of the genitalia may be tabulated as follows : 



Rec. sem. Prostate Penis-sac Penis 



Penis. Penis-sac. duct. duct. Vas. def. retractor, retractor. Shell. 



7.50 6.00 6.50 6.50 17.00 2.10 2.15 29.00 



9.00 6.00 6.00 5.50 15.00 4.50 5.00 31.00 



9.00 7.00 6.00 7.00 15.00 4.50 5.00 31.50 



The penis-sac retractor is peculiar (pi. XII, fig. F) ; for about 

 half of its length it is a narrow band of muscle; at this point it sud- 

 denly enlarges, forming a thick pad-like structure, which bifurcates 

 unequally, continuing to the penis-sac in two wide, flat bands of muscle, 

 which enter the penis-sac by several branches. (Dissection No. 23085 

 and 23086.) 



The genitalia of the Lincoln Park auricularia is similar to Eisig's 

 figure (Zeitsch. Wissen. Zool., XIX, p. 29), the organs, however, not 

 being shown in much detail in his figure, but their relative shapes are 

 similar. Moquin-Tandon's figure (Hist. Nat. Mol. Ter. Fluv. Fr.) 

 shows the organs apparently as in their natural position and the female 

 organs as they appear when swollen with water. None of these figures 

 c how the male organs and their muscles in a clearly defined manner. 



RANGE: Europe and northern Asia; North America (introduced). 



RECORDS: Lincoln Park, Chicago, Ills., in greenhouse (Baker); Flatbush, 

 Brooklyn, N. Y. (Call; Smith). 



GEOLOGICAL RANGE: Not recorded. 



ECOLOGY: Auricularia is a mollusk which prefers slow-moving 

 bodies of water like lakes, ponds and the still parts of rivers. In cap- 

 tivity it remains near the bottom of the aquarium, rarely coming to 

 the surface. It is rather active, moving about the aquarium with a 

 steady gliding motion. 



REMARKS : The specimens of auricularia from the greenhouse in 

 Lincoln Park seem typical, though some old specimens approach var. 

 ventricosa Hartm. The old specimens differ greatly from the half- 

 grown ones, the outer lip widely expanding and forming a peculiar 

 extension of the aperture at its posterior end, like a rude canal. Some 

 specimens recall Radix ampla Hartm. 



