THE NAUTILUS. 



125 



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

 54-57 (Eurynia lienosa, E. subrostrata, and Lampsilis ventricosa 

 satur). 



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

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

 loma leivisii. 



Walker, "Apical Characters in Somatogyrus, with Descrip- 

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

 49-53. Description of Somatogyrus wheeleri, and S. amnicoloides. 



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

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

 Arkansia (genus) and Arkansia wheeleri. 



Note. — The paper of E. G. Vanatta entitled, " Unionidse 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. 



DESCRIPTIONS OF NEW SPECIES OF MOPALIA AND TRACHYDERMON. 



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 

 strias 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, 



