Suhjamilies, Genera, and Subgenera — Recent and Fossil 157 



cially in those organs like the nidamental gland, the uterus and the oviduct, 

 which may become swollen and thus alter the true form of these organs. 



Three species of Carinijex have been dissected by Pilsbry and the 

 writer, ponsonbyi, jacksonensis, and newberryi subrotunda, and all show 

 the homogeneity of the group and its distinctness from Helisoma. 



Respiratory and Renal Systems. The pseudobranch (plate 34. fig. 1) 

 of ponsonbyi is a rounded extension from the rectal region, in form like that 

 in Helisoma, including the rectal ridge which extends over the pseudo- 

 branch. In jacksonensis (plate 35, fig. 4), the pseudobranch is narrower. 

 In the specimen figured, the pseudobranch was folded in such a manner as 

 to make the ridge appear on the left margin of the organ. 



The kidney (plate 45, fig. 2) is long and narrow (15 mm. long, 1 to 1.2 

 mm. wide) and the ureter is reflexed at right angles to the kidney. A sec- 

 tion of the kidney near the middle (fig. 12) shows it to be much flattened, 

 with a bottle-shaped lumen and roundly elongated, and flattened veins. 

 There is no superposed ridge like that in Helisoma. The ridge on the mantle 

 to the left of the kidney is seen in the section to be flattened and wide. 



Digestive System. The digestive system is similar to that of Pierosoma. 

 The stomach region is shown on plate 48, fig. 3. The intestine is looped 

 about the stomach and liver. The buccal sac is similar to that organ in 

 Helisoma. 



The jaw is peculiar. There is but one jaw which is horseshoe-shaped, 

 narrow, composed of many small, vertical plates which produce a saw-like 

 edge. In ponsonbyi (plate 49, fig. 19), there are spiral striae on the jaw 

 plates. In jacksonensis this striation is not visible (plate 49, fig. 18). The 

 jaAV is attached to a very large cartilage which has the relative shape and 

 size shown in fig. 17. In fig. 19, the jaw is somewhat distorted. The jaw of 

 Carinijex bears some resemblance to the fragmented jaw of the Planor- 

 binae, but the general form is different. 



Radula. The radula of Carinijex ponsonbyi (plate 67, fig. 8) has a 

 square, bicuspid center tooth, the spade-shaped cusps extending below the 

 lower border of the base of attachment. The lateral teeth (1-6) are tri- 

 cuspid, all cusps sharply spade-shaped, including the mesocone. In some 

 rows, single cusps may become bifid, as the ectocone in the fifth lateral 

 tooth in fig. 8. The intermediate teeth (7-8) differ only in the splitting of 

 the ectocone into two sharp cusps. The marginal teeth (9-27) are long and 

 narrow, the entocone remaining unchanged at first (9-10) but the 

 ectocone undergoing additional splitting. On the eleventh tooth the ento- 

 cone begins to split, developing three small, sharp cus})s. In the outer 

 part of the membrane, the marginal teeth become narrower and the ento- 

 cone splits into seven very small, sharp cusps and the ectoconic area 

 becomes simply serrated along the outer margin. The mesocone remains 

 unchanged throughout the entire row. 



In Carinijex jacksonensis (plate 65, fig. 4), the teeth have practically 

 the same shape, but are smaller. There are ten lateral teeth and two 

 intermediate teeth. In the splitting of the marginal teeth, the inner cusp 

 of the entocone is larger than the four cusps on the inner side of the 

 mesocone. This feature persists throughout the radula. Tlic radula formulae 

 of the two species are as follows: 



ponsonbyi 32-1-32 Klamath Lake, Oregon 210-217 J. Henderson 



jacksoijensis 25-1-2.5 Jackson Lake, AVyoming 215-221 J, Henderson 



