PACIFIC COAST SPECIES. 125 



Dupetithouarsi ; 6 in NicMiniana; G in redimita; 6 in exarata; 5 in 

 Diahloensis; about 7 in Carpenteri ; 3 in ramentosa ; 5 in Ayersiana ; 

 5 in Californiensis ; 4-6 in sequoicola; 8 in Traski; 8 in facta; C in 

 Kelletti; 9 of unequal size in Stearnsiana. The jaw of ruficincta differs 

 in having over 10 ribs covering its whole surface, and in being only 

 slightly arcuate. I have not examined the tj pica! intercisa, of which, 

 however, redimita is a variety. 



The lingual membrane is long and narrow, arranged as in Patula. 

 The characters of the individual teeth are shown in my plates. In 

 Figs. O, P, R, S, and U of Terr. Moll., V, Plate IX, the gradual change 

 from central through laterals to the extreme marginals is shown. The 

 central teeth have a base of attachment much longer than wide, with 

 incurved lower margin and expanded lower lateral angles ; the upper 

 margin broadly reflected ; reflection short, stout, with subobsolete side 

 cusps, bearing no cutting points, and a stout, long median cusp, bear- 

 ing a short, blunt cutting point, which does not reach the lower margin 

 of the base of attachment; the reflection with the median cusp is pear- 

 shaped; in many species there is a duplicate line of re-enforcement 

 parallel to the upper margin of the base of attachment. The lateral 

 teeth are of similar type to the centrals, but are asymmetrical by the 

 suppression of the inner, lower, lateral angle of the base of attachment. 

 The outer laterals have a side cusp and cutting point. The transition 

 from laterals to marginals is formed by the greater proportional devel- 

 opment of the cutting point, the lesser development of the cusp ; the 

 cutting point then becomes bifid, the reflection becomes more nearly 

 the same size as the base of attachment, and thus the true marginals 

 are gradually reached. These last are longer than wide, have a base 

 of attachment smaller than the reflection, and cut away on its lower 

 inner angle ; the reflection is produced into one long, sharp, oblique, 

 bifid cutting point, the inner division the smaller, and one outer, much 

 shorter, sharp, rarely bifid cutting point. 



Most of the species examined agree in dentition with this descrip- 

 tion. Some have more blunt cutting points to their marginals, as 

 sequoicola (Terr. Moll., V, Plate IX, Fig. J), but even on various parts 

 of the same membrane the marginals vary in this respect. In Kelletti, 

 Stearnsiana, tudiculata, arrosa, TrasM, sequoicola, Ayersiana, redimita, 

 Nickliniana, ramentosa, exarata, Diahloensis, facta, Garpenteri, I have 

 failed to detect any side cutting points to the central and inner lateral 



