THE NAUTILUS. 27 



ELLIPTIC RAVISTELLUS (Morelet). ( Nephronaias rav. Simpson, 

 '14, p. 283). 



Specimens from Lake Yzabal, at Jocolo, Guatemala, are at 

 hand, collected by A. A. Hinkley in January, 1914. Among 

 them are 1 male, and 3 females with soft parts; one of the 

 females is gravid, but has only eggs, no glochidia. Seven 

 others from Lake Yzabal were collected January 9, 1917; among 

 them 1 male, and 6 gravid females, three of them with glo- 

 chidia. 



The identification is undoubtedly correct, and has been made 

 chiefly according to v. Martens (Biol. Centr. Amer. Moll. 1900, 

 p. 516, pi. 38 f. 2). The color of the nacre, in my specimens, 

 varies from white through lead color and pinkish to dull purple. 

 The breeding season seems to be similar to that of the preced- 

 ing species (eggs and glochidia in January). 



The anatomy resembles that of E. ortmanni,, but the posterior 

 margins of the palpi are connected at their bases only, and re- 

 markably enough, the inner lamina of the inner gills, in all 

 specimens before me, is free from the abdominal sac only for 

 about one-half of the length of the latter (or very slightly more), 

 while it is connected with it in the anterior half (or slightly 

 less). This is a rather unusual condition in American Union- 

 inae. Of course, in this case, this character cannot be regarded 

 as essential, before a larger number of Central American shells 

 have been investigated. 



Gills, marsupium, and placentae of the Elliptio-type. Glo- 

 chidia absolutely identical with those of E. ortmanni and cala- 

 mitarum : L. 0.23, H. 0.22 mm. Color of soft parts (in alco- 

 hol) pale, with black pigment in the region of the branchial, 

 anal, and supraanal openings. 



NOTES. 



UR. PAUL BARTSCH spent part of May and June in the 

 Bahamas and Florida, continuing- his studies of Cerion. 



DR. C. MONTAGUE COOKE, who has been working on the 



