THE NAUTILUS. 125 



141, 142 (Carunculina texasenm, and C. glans), Ditto, XXX, 

 54-57 (Eurynia lienosa, E. 8ubro8trata, and Larapsilis ventricosa 

 satur). 



Walker, "On Paludina coarctata and incrassata, Lea". 

 Nautilus, Vol. XXVIII, pp. 121-127. Description of Campe- 

 loma lewisii. 



Walker, "Apical Characters in Somatogyrus, with Descrip- 

 tion of Three New Species." Nautilus, Vol. XXIX, pp. 37-41, 

 49-53. Description of Somatogyrus v)heeleri, and S. amnicoloides. 



Walker and Ortmann, "A New North American Naiad", 

 Nautilus, Vol. XXV, pp. 97-100, PI. VIII. Description of 

 Arkansia (genus) and Arkansia wheeleri. 



NoTK. — The paper of E. G. Vanatta entitled, " Unionidae from Southeast- 

 ern Arkansas and N. E. Louisiana", Nautilus, Vol. XXIII, pp. 102-104, 

 should be compared for a list of species reported from the lower Ouachita, some 

 of which may be yet located in Clark County sections of the river. 



OESCBIFTIONS OF NEW SPECIES OF MOPALIA AND TBACHTDEBMON. 



BY HENRY A. PILSBRY. 



Mop alia lowei n. sp. 



The chiton is rather small, oblong, moderately elevated, 

 carinate, the lateral slopes straight. The valves are irreg- 

 ularly mottled with ferruginous, sea-green and olive. The 

 anterior valve has ten radial ribs, those at the suture bearing 

 compressed tubercles, the others rounded tubercles. The in- 

 tervals are also tuberculose, with some interstitial granula- 

 tion. Valves ii to vii have low, tuberculose sutural and diag- 

 onal ribs, the lateral areas tuberculose and granular. Central 

 areas with the jugal tract closely striate longitudinally, the 

 striae converging forward near the beaks, elsewhere sub- 

 parallel, but slightly irregular in places. Pleural tracts hav- 

 ing longitudinal ribs, near the ridge converging forward 

 somewhat, becoming divergent towards the lateral borders. 

 These are intersected by a system of much weaker curved 

 ribs radiating forward and laterally, forming oblong tuber- 

 cles on the longitudinal ribs. The posterior valve is short, 



