296 Annals of the Carnegie Museum. 



Of this form I have only the soft parts, and their structure is like 

 that of other species of this genus. The mantle-connection between 

 anal and supra-anal is almost as long as the anal, and the supra-anal 

 is only slightly longer than the mantle-connection. The anal is 

 finely crenulated, and the branchial has papillae. Posterior margins 

 of palpi connected for a short distance. Inner lamina of inner gills 

 free. Anterior end of inner gill about half-way between the palpi 

 and the anterior end of the outer gill. 



Marsupium as usual, with distended edges, and secondary water- 

 tubes. Glochidia as small as in the foregoing species, and of the same 

 shape. Length 0.30; height 0.25 mm. (see Plate XIX, fig. 4). 



Color whitish, edge of mantle spotted with black and white in the 

 region of the branchial, anal, and supra-anal. Marsupium brown. 



I have had no opportunity to examine the shell of this species, but 

 it seems that it is related to A. heterodon. 



Alasmidonta undulata (Say). 



Numerous specimens from the Atlantic drainage in eastern Penn- 

 sylvania have been in my hands. 



The breeding season begins in the middle of July, and lasts till the 

 aniddle of June, so that the end of one season, and the beginning of the 

 next are not very far apart. Of specimens found in July, 1 8th and 

 22d, all had only eggs; while those found on June 14 (only two) had 

 fully developed glochidia. 



Soft parts typical. Mantle-connection between anal and supra-anal 

 rather long, slightly longer than the anal and than the supra-anal. 

 Branchial with papillae, anal crenulated. Posterior margins of palpi 

 connected for one-half or slightly less than one-half of their length. 



Diaphragm normal. Inner lamina of inner gills entirely connected 

 with the abdominal sac, and only in a few cases was a small hole ob- 

 served at the posterior end of the foot. Anterior end of inner gill 

 about half-way between the outer gill and the palpi. 



Marsupium normal; when charged, having distended edges, secon- 

 dary water-tubes, and undivided ovisacs. Glochidia (Ortmann, 191 lb, 

 pi. 89, fig. 9) moderately large, higher than long, with strong hooks. 

 Length 0.34; height 0.36 mm. 



Abdominal sac whitish; foot paler or darker orange-brown; palpi 

 whitish to orange-brown. Gills grayish brown, shading into orange. 

 Mantle transparent gray, shading into brownish or brownish orange 



