170 TERRESTRIAL AIR-BREATHING MOLLUSKS. 



the marginals is made in Ingersolli and incrustata without the splitting of the 

 inner cutting point, but it is otherwise in vortex and iurbiniformis. The margi- 

 nals are low, wide, the inner cutting point is long, blunt, simple in Ingersolli 

 and incrustata, bifid in the other species. The outer cutting points of all are 

 short, varying in number from 1 to 3. 



Thus in this genus, as in most of the others, we find a certain range of varia- 

 tion in the dentition and jaw. 



From the above comparisons I have omitted ]\I. Lansingi, whose puzzLng 

 combination of jaw and marginal teeth is described below. 



Microphysa incrustata, Poey. 

 Vol. HI. PL XXIX. a, Fig. 4. 



Shell umbilicated, depressed, smooth, horn-colored, usually incrusted with 

 dirt, with crowded stria? ; spire slightly elevated, composed of 4 or 5 well- 

 rounded whorls separated by a deeply impressed suture ; beneath with a broad 

 umbilicus, one third the diameter of the shell, exhibiting all the whorls within ; 

 aperture circular, being but slightly impinged upon by the penult whorl, its ex- 

 tremities joined by a slightly appressed scale of enamel, rendering the peri- 

 stome continuous; peristome slightly reflexed, so as to render the aperture 

 somewhat campanulate. Greater diameter 4 J, lesser 4 mill. ; height, 2 null. 



Helix incrustata, Poey, Memorias, I. 208, 212, PI. XII. Figs. 11-16. — Pfeiffer, 

 Mon. Hel. Viv., III. 632. — W. G. Bixney, Terr. Moll., IV. 68, L. & Fr.- 

 W. Sh., I. 70, Fig. 117 (1869). 



Helix saxicola, Gould in Terr. Moll., II. 174, Fl. XXIX. a, Fig. 4, not 

 Pfeiffer. 



Helix incrassata, Reeve, Con. Icon., 972. 



Pscuddhyalina incrustata, Tryon, Am. Journ. Conch., II. 265 (1866). 



Galveston and Corpus Christi, Texas. Also near Havana, Cuba. It must be 

 considered a species of the Southern Region. 



Its circular, campanulate aperture, almost disconnected with the preceding 

 whorl, is one of its most striking peculiarities. 



Jaw low, wide, slightly arcuate, ends blunt, but little attenuated ; anterior 

 surface with numerous crowded ribs, bluntly denticulating the lower mar- 

 gin. 



Lingual membrane with 13 — 1 — 13 teeth, of which 5 are perfect laterals. 

 Centrals quadrate, tricuspid ; laterals like centrals, but bicuspid ; marginals 

 low, wide, with one inner long, blunt, and several short, side, blunt cutting 

 points (PI. III. Fig. S). 



I formerly placed this species in Patula, but, having recently examined the 

 jaw of a dried specimen in my cabinet (collected over thirty years ago at Gal- 

 veston), I am led to believe that Von Martens is right in placing it in Micro- 

 physa. 



