SubfaffiUies, Genera, and Subgenera — Recent and Fossil 147 



In another large species of Pierosoma from Klamatli Lake, Oregon 

 (occidcntalc, plate 61, fig. 1), the teeth are more uniform with but little 

 splitting of the cusps. The radula differences between the two species 

 occidentale and traskii are very marked, as shown on plates 60 and 61. 



In specimens of tenue calif orniense from Shandon, California (plate 63, 

 fig. 2) , the center tooth has two wide, spade-shaped cusps- extending below 

 the base of attachment. The laterals (1-11) are at first wider than high, 

 the cusps rather short, but toward the marginal teeth they become nar- 

 rower. The entocone and the ectocone tend to split in some teeth (as 1, 3, 

 6, 7). There is one narrow intermediate tooth (12). The marginal teeth 

 (13-19) are narrow, the entocones 4-6 cuspidate. In the 100th row of 

 the same membrane, the entocone and ectocone of the lateral teeth were 

 largely modified by splitting (see fig. 2). 



In a radula from a specimen living in the San Bernardino Mountains, 

 there were eleven laterals, one intermediate tooth " and nine or more 

 marginals. No splitting was observed in this radula but in another mem- 

 brane all of the laterals were abnormal (plate 59, fig. 4) in the sixtieth 

 row, small cusps appearing irregularly on the entoconic region. The en- 

 tocone of the first lateral was broken up into four small cusps. The inter- 

 mediate and marginal teeth were narrow and many of them abnormal in 

 the splitting of the entocone (as 14, 16, 17). The mesocone in all teeth 

 was more or less irregular. In fig. 6, a very abnoniial eleventh tooth from 

 another specimen is figured. The relatively small species oregonense (plate 

 61, fig. 3) has narrow laterals (1-8) and intermediate teeth (9-10). The 

 marginals are normal for the group. 



The radula formulae of the different species vary more or less and the 

 individual radulae may differ in number of teeth in a row. For comparison 

 all of the species of Pierosoma which have been examined, together with 

 all of the localities represented, are shown in the following table. This 

 also indicates the material studied and the source from which the material 

 was obtained. ]\Iore specimens were dissected for the genitalia than for the 

 radulae. From one to seven specimens of each were examined. 



Species 

 trivolvis 

 trivoli'is 

 trivolvis 

 trivolvis 

 trivolvis 

 pseiidotrivolvis 



( =le}itum) 

 pseudotrivolvis 

 pseudotrivolvis 

 pseudotrivolvis 

 pseudotrivolvis 

 pseudotrivolvis 

 lentum 

 fallax 



macrostotnum 

 viacrostomum 

 macrostomum 

 macrostnmum 

 chautnuquense 

 truncatum 

 winslowi 



Formulae 

 23-1-23 to 26-1-26 

 23-1-23 to 24-1-24 

 23-1-23 to 24-1-24 

 23-1-23 to 25-1-25 

 23-1-23 to 24-1-24 

 23-1-23 to 24-1-24 



Locolity 

 Canandaigua L., New York 

 Green Lake, Wisconsin 

 Devils Lake, Wisconsin 

 Murphy Creek, Wisconsin 

 Sturgeon Bay, Wisconsin 

 St. Joseph, Illinois 



24-1-24 to 25-1-25 Peoria, Illinois 



22-1-22 to 24-1-24 Reelfoot L., Tennessee 



23-1-23 to 24-1-24 Mammoth Spgs., Arkansas 



24-1-24 Ada Lake, Oklahoma 



23-1-23 to 25-1-25 Trinity R., Texas 



26-1-26 to 28-1-28 New Orleans, Louisiana 



26-1-26 to 28-1-2S Near Boston, Massachusetts 



27-1-27 to 30-1-30 Bayfield, Wisconsin 



27-1-27 Moose Ear Creek, Wisconsin 



31-1-31 to 32-1-32 Saskatoon, Canada 



37-1-37 to 39-1-39 L. Grauveau, Canada 



24-1-24 to 26-1-26 Chautauqua L., New York 



20-1-20 to 21-1-21 Winnel)ago L., Wi-sconsin 



27-1-27 to 29-1-29 Arbor Vitae L., Wisconsin 



