OF CONCHOLOGY. 235 



ness, and without impressed striae. It is often nearly as dark 

 colored as Jidelis, though usually paler, and, if it is not uniform, 

 it is its under side that is the palest, not the upper. It has the 

 Jidelis bands beautifully developed, and may be considered a 

 branch from the species also. In one small district only, near 

 its southern limit, is it angled and hirsute, but still retains its 

 bands, becoming now the Hillebrandi. South of the present 

 known range of infumata is an interval of 50 miles, without any 

 representative of jidelis. Then we come to the small tract in- 

 habited by sequoicola, in which we find characters similar to 

 Mormonum, but more elevated form, more permanent (though 

 deciduous) bristles, and larger size. Twenty-five miles farther 

 south, without connecting forms, and we find the well-known 

 Dupetitliouarsi, differing from Jidelis in small size, uniform color, 

 and, instead of striae, faint malleation. Another interval of 110 

 miles over a little explored region, and we find Traskii, like the 

 last in form, but very pale in color (often palest below), and with 

 the striae of Jidelis. All these, except Dupetitliouarsi, have also 

 lost one whorl, having 6 or 6h On Sta. Cruz I., opposite the habi- 

 tat of Traskii, we find Ayresiana, higher in form, with one more 

 whorl, but otherwise showing its alliance plainly, separated by 

 the sea for 25 miles. Across another watery interval of 65 

 miles to Catalina I., and we find rufocincta much like Traskii, 

 but more depressed and smaller, its apex compactly rounded off. 



Here, too, we find a smaller race (Gfabbi), ^jthout the striae, 

 but apparently formerly connected by intermediate sizes, which 

 may be now extinct. And on three of the islands we have one 

 equally small, but more numerous, the striae visible, but the spire 

 so rounded, and umbilicus so nearly covered, that it would seem 

 very far from Jidelis, if we had not traced its relationship through 

 so many forms. Again visiting the mainland 75 miles distant 

 at San Diego, and 120 miles southeast of the supposed limit of 

 Traskii, we find commencing a form closely allied to it but re- 

 ferred to Remondii, first sent from Guaymas, Mexico. This, 

 Mr. Gabb has traced southward to the coast opposite Guaymas 

 on the west side of the Gulf, in lat. 27°, where it runs into a 

 subangled, probably hirsute form called Lohrii*, closely resem- 

 bling Rowelli, and the analogue of Hillebrandi. 



From the occurrence of Remondii, at Guaymas, we trace the 

 group into Mexico, and probably others will be found to repre- 

 sent it there. I have suggested that it extends into Texas under 



co 



the forms of griscola and Berlandieriana, but further mvestiga- 



* H. Lohrii is uot hirsute, but polished. I have seen fresh specimens. 



W. M. G. 



