NO. 1205. SYNOPSIS OF THE NAIADES— SIMPSON. 597 



tNEPHRONAIAS PLICATULUS Charpentier in Kuster. 



* Unio plicatulus Charpentier in Kuster, Conch. Cab. Unio, 1856, p. 154, pi. 



XLiv, fig. 4.— *FiscHER and Crosse, Miss. Sci., Ft. 7. 11, 1894, p. 598. 



Mexico. 



tNEPHRONAIAS RAVISTELLUS Morelet. 



* Unio ravistellus Morelet, Test. Noviss., No. 1, 1849, p. 29. — *Kuster, Conch. Cab. 



Unio, 1856, pi. XLii, fig. 6.— *B. H. Wright, Check List, 1888.— *PiETEL, 

 Conch. Sam., Ill, 1890, p. 165. — *Fischer and Crosse, Miss. Sci., Pt. 7, II, 

 1894, p. 609, pi. LXi, figs. 4, 5, and 5a. 

 * Margaron ( Unio) ravistellus Lea, Syn., 1870, p. 40. 



Guatemala. 



tNEPHRONAIAS VELLICATUS Reeve. 



* Unio vellicatus Reeve, Conch. Icon., XVI, 1865, pi. xxii, fig. 103. — ^B. H.Wright, 



Check List, 1888.— ^'PiETEL, Conch. Sam., Ill, 1890, p. 171. — *Fischer and 

 Crosse, Miss. Sci., Pt, 7, II, 1894, p. 610. 



Guatemala. 



NEPHRONAIAS MELLEUS Lea. 



* Unio melleus Lea, Pr. Ac. N. Sci, Phila., XI, 1859, p, 152; *J1. Ac, N. Sci, Phila,, 



IV, 1860, p. 250, pi. xxxviii, fig. 129; *0b8. VII, 1860, p, 68, pi, xxxviii, fig. 

 129.— *Reeve, Conch. Icon., XVI, 1865, pi. xxi, fig. 92.— *^P^tel, Conch. 

 Sam.,III, 1890,p. 158. 



* Margaron ( Unio) melleus Lea, Syn., 1870, p. 35.' 



Mexico or Central America, no doubt. 



GENUS GLEBULA Conrad 1853. 



(Type, Unio rotundata Lamarck.)- 



Glehula Conrad, Pr. Ac. N. Sci. Phila., 1853, p. 268. 



Shell solid, much inflated, short elliptical, bluntly pointed and slightly 

 biangulate behind, with a low, posterior ridge; female shell swollen at 

 post base; beaks compressed, the sculpture not seen; epidermis brown- 

 ish, clothlike; pseudocardinals divided into irregularly radiating, gran- 

 ular lamina, sometimes to the number of a dozen or more in each valve; 

 hinge plate reduced to a mere rounded line behind the pseudocardi- 

 nals; laterals short, remote, anterior adductor scars deep, smooth; 

 there is in each valve only a single, large, semicircular posterior scar 



' I am not certain just where this and the preceding species should be placed. 

 This remark can be applied to a number of other forms placed in this genus. 



- 1 have examined a number of animals of the only species of this curious genus, 

 but regret that they were badly decayed, and that none were gravid. In one speci- 

 men several ovisacs were distended with gas, and these were separated by a deep 

 sulcus. This fact, the union of the inner gills with the abdominal sac, and the post- 

 basal swelling seen on some shells incline me to believe that it is a highly organized 

 species. 



