REPRODUCTION AND ARTIFICIAL PROPAGATION OF FRESH-WATER MUSSELS. Iiq 



ana) ; Elliptio Rafinesque (established for the North American species of Unio to dis- 

 tinguish them from the European). 



2. Anodontinae. "Marsupium formed by the outer gills in their whole length, 

 distending when charged, and the thickened tissue at the edge capable of stretching out 

 in a direction transverse to the gill, but not beyond the edge (or only slightly so) ; water 

 tubes in the gravid female divided longitudinally into three tubes, with only the one in 

 the middle used as an ovisac, and closed at the base of the gill." 



The following genera are grouped under this subfamily: Alasmidonta Sa)', Stro- 

 phitus Rafinesque, Symfyhynota Lea, Anodonfoides Simpson, Anodonfa Lamarck. 



3. Lampsilinae. "Marsupium rarely formed by the whole outer gill, generally only 

 by or within the posterior part of the outer gill; edge of marsupium, when charged, dis- 

 tending, and bulging out beyond the original edge of the gill, generally assuming a 

 beaded appearance; water tubes simple in the gravid female." 



The following genera are grouped together under this subfamily: Ptychobranchus 

 Simpson, Ohliqnaria Rafinesque, Cyprogenia Agassiz, Obovaria Rafinesque (including 

 Lampsilis ligamentina) , Plagiola Rafinesque, Parapiera gen. nov. (established for Lamp- 

 silis gracilis), Proptera Rafinesque (established for Lampsilis alata, piirpuraia, Iccvis- 

 sima), Lampsilis Rafinesque (including Micromya f abatis), Truncilla Rafinesque. 



It will be seen by a comparison of the genera which Ortmann assigns to his three 

 subfamilies with the several groups of Simpson, that the most significant change intro- 

 duced by the former arrangement is the disruption of Simpson's Homogenae and a 

 redistribution of its genera and those of the Digense, Diagena;, and Tetragenge among 

 the subfamilies Unioninse and Anodontinae, the former receiving all of the genera con- 

 sidered by Ortmann, except Alasmidonta, Strophitus, Symphynota, Anodontoidet, and 

 Anodonta, which, bj' reason of the peculiar secondary division of the water tubes of the 

 gravid female in all of these genera, he insists should be placed in a subfamily by them- 

 selves. Apparently his grounds for the rearrangement are sound. In the Lampsilinae 

 are included all of the genera of Simpson's Heterogenee, together with those of the 

 MesogcuK, Ptychogens, and presumably the Eschatigenae — a procedure which is in 

 harmony with the suggestion made above that the genera in which a differentiated 

 portion only of the outer gill functions as a marsupium should be grouped together. 



The reader is referred to Ortmann's monograph for further details and for the con- 

 siderations which have led him to shift a number of species from one genus to another 

 and to establish certain new genera, while renaming others. 



This system has the merit of being based upon a careful study of the anatomy of 

 the species with which he has been concerned, and he has clearly demonstrated the 

 fact that shell characters alone are not sufficient for a determination of true relation- 

 ships. To what extent his classification will replace Simpson's remains of course to be 

 seen, but in any future discussion of the matter the new facts brought to light by Ort- 

 mann in his study of the structural modifications of the marsupium must be reckoned 

 with. 



