362 ANNALS OF THE CARNEGIE MUSEUM. 
ro1tb. ORTMANN, A. E. Monograph of the Najades of Pennsylvania. I. Ana- 
tomical Introduction. The System of the North American Najades 
(Mem. Carnegie Mus., 4, pp. 279-347, 4 plates). 
I9t1c. ORTMANN, A. E. The Classification of European Najades (Nautilus, 25, 
Pp. 5-7, 20-23). 
1908. Pitsspry, H. A. and Frierson, L. S. Description of a Mexican Lampsilis 
(Nautilus, 22, pp. 81-82). 
1909. Piuspry, H. A. Unionide from the Panuco River system, Mexico (Pr. Ac. 
Nat. Sci. Philadelphia, pp. 532-539). 
1889. ScHIERHOLZ, C. Ueber Entwicklung der Unioniden (Denkschr. kais. Akad. 
Wiss. Wien. Math.- naturw. Cl. 55, pp. 183 ff.). 
1892. Simpson, C. T. Notes on the Unionide of Florida and the Southeastern 
States (Pr. U. S. Mus., 15, pp. 405-436). 
1898. Simpson, C. T., in Baker, see Baker, F. C. 
1900a. Simpson, C. T. New and Unfigured Unionide (Pr. Acad. Nat. Sci. Phila- 
delphia, 52, pp. 74-86). 
1900b. Simpson, C. T. Synopsis of the Najades, or Pearly Freshwater-mussels 
(Pr. U. S. Mus. 22, pp. 501-1044). 
1898. STERKI, V. Some Observations on the Genital Organs of Unionide, with 
Reference to Classification (Nautilus, 12, pp. 18-32). 
1903. STERKI, V. Notes on the Unionide and their Classification (Americ. 
Natural., 37, pp. 103-113). 
1907. STERKI, V. (Note on Tritogonia tuberculata.) (Nautilus, 21, p. 48.) 
1909. THIELE, J. Mollusca, in Brauer, Die Suesswasserfauna Deutschlands, 
Heft 19, pp. 1-46. 
1910. VANATTA, E. G. Unionide from Southeastern Arkansas and Northeastern 
Louisiana (Nautilus, 23, pp. 102-104). 
1855. WauL, E. von. Die Suesswasser-Bivalven Livlands (Arch. Naturk. Liv., 
Ehst- und Kurlands., ser. 2, vol. 1, pp. 75 ff.). 
1910a. WALKER, B. The Distribution of Margaritana margaritifera in North 
America (Pr. Malacol. Soc., 9). 
1910b. WALKER, B. On the validity of Unio undatus Barnes (Nautilus, 24, pp. 
6-10, 16-24). 
1910c. WALKER, B. Notes on Truncilla, with a Key to the Species (Nautilus, 24, 
pp. 75-81). 
EXPLANATION OF PLATE XVIII. 
Anatomy of Najades: sections of gills. 
Photographed with Bausch & Lomb Objective, 32 mm. 
Fic. 1. Quadvula lachrymosa (Lea). Sterile female-—Ohio River, St. Marys, 
Pleasants Co., W. Va., coll. Sept. 20, 1910.—Carn. Mus., No. 61, 4,541. Horizontal 
cross section through left inner (7) and outer (0) gill, showing marsupial structure 
in both gills. 
Fic. 2. Pleurobema riddelli (Lea). Sterile female—Pearl River, Jackson, 
Hinds Co., Miss., A. A. Hinkley coll., Nov. 5, 1910.—Carn. Mus., No. 61, 4,963. 
Horizontal cross section through left inner (7) and outer (0) gill, showing marsupial 
structure only in outer gill. 
