130 THE NAUTILUS. 



Subfamily : Hyriinse. Anal closed above. Marsupium with 

 interrupted interlamellar connections, standing in rows, and forming 

 incomplete, communicating water tubes. Non-marsupial gill with 

 poorly developed, scattered interlamellar connections. Larva a 

 glochidium. (ffyria, Tetraplodon, Diplodon, Castalina.) 



Subfamily : Mutelinae. 1 Anal open or closed above. Marsupium 

 with well-developed, continuous septa, forming well-defined wafer 

 tubes. Non-marsupial gills also with distinct water tubes. Larva a 

 lasidium. (Spatha, Glabaris, Fossula, Monocondylcea.} 



(8) Our chief attention should now be directed to the study of 

 further genera from Africa and Asia, and also the European forms 

 should be more closely investigated. 



EXPLANATION OF PLATES. 



Plate VI. 



Diagrammatic side views of the soft parts of Naiades, with the left 

 half of the mantle removed along the mantle-attachment line, show- 

 ing the arrangement of palpi, gills, diaphragm, anal, supraanal and 

 branchial openings. 

 In all figures the letters indicate : 

 m. Right half of mantle. 

 ml. Mantle-attachment line, 

 ami. Ascending part of mantle-attachment line, 

 f. Foot, 

 p. Palpi, 

 i. Inner gill. 

 e. Outer gill, 

 sa. Supra-aual opening, 

 an. Anal opening, 

 b. Branchial opening. 

 d. Diaphragm. 



x. Mantle connection in front of branchial opening. 

 Fig. 1. Margaritana margaritifera (L.). Specimen from Indian 

 Run, Rene Mont, Schuylkill Co., Pa. 



Fig. 2. Quadrula subrotunda (Lea). Specimen from Allegheny 

 River, Kelly, Armstrong Co., Pa. 



Fig. 3. Unio gibbosus Barn. Specimen from Little Beaver Creek, 

 Enon Valley, Lawrence Co., Pa. 



Fig. 4. Parreysia wynegungaensis (Lea). Specimen from Bombay, 

 India. 



Fig. 5. Spatha kamerunensis Walk. Specimen from Kamerun, 

 Africa. 



1 The nomenclature depends on the knowledge of the genus Mutela. 



