NO. 1-56. FOSSIL SHELLS OF THE COLORADO DESERT— STEARNS. 281 
Third. A connecting' link between the above and the cancellated 
forni.s — that is to say, forms that are sculptured both transverseh' and 
longitudinally — as seen in fig. 12. Robust, angulated, spirally lirate, 
and longitudinally plicate on the third and fourth whorls from the tip 
of the apex; the eccentric character of the aperture makes this a 
unique example. In fig. 5 is presented a slenderer form with the chief 
sculpture characters of fig. 12. In this the threading of the penulti- 
mate whorl is inconspicuous, increasing in prominence on the three 
whorls above, which are also strongl}" ribbed longitudinally; the whorls 
are rounded above. 
Fourth. Longitudinal sculpture strongest. In all of the following- 
examples the spiral sculpture is seen and is more or less conspicuous. 
This character varies, however, in figs. 6 and l-l; the lir^e are numerous 
and closely, evenly placed; in these also the shells are slenderer, and 
the longitudinal ribs cross the spiral threading without interruption. 
In fig. 6 it will be noticed the whorls are convex, in fig. 14 somewhat 
angulated above, and the mouth in the latter is small. No. 5, in the 
third group, might be included here, perhaps, as appropriately as 
where I have placed it. 
Fifth. Cancellated and nodose sculptures are the prominent features 
in the forms here included. The whorls in all are angulated above; 
the spiral threadings vary in number, and where crossed b}" the 
lengthwise ribs become tul)erculated or nodose. In fig. 13 is seen a 
repetition of the slenderer aspect, and in fig. 18 is shown the maxi- 
mum of robustness. On the basal w^horl, close-set fine threading 
below, above a double threading is a conspicuous feature, with wider 
interspaces, which extends to the upper whorls. 
In figs. 15 and 16 are examples intermediate in size and other 
I'haracters. A ventricose example is presented in tig. 17, distinctly 
but not strongly threaded with man}" of the features of No. IS; in 
this the longitudinal sculpture is only suggested. 
These filose, cancellated, and tuberculated varieties call to mind 
familiar forms ])elonging to the American Strejjomatidm^ which, no 
doubt, were in Conrad's mind when he described certain aspects of 
the shells herein reviewed as Melania exlgua. 
Orcutt's recent examples, collected b}" him at the Fish Springs 
locality, contained in the U. S. National Museum (No. 10-1886), are not 
figured ; in these the surface is finely granulose. As only a small 
number of shells from the Orcutt localities have been examined, it is 
not known whether the springs visited by Mr. Orcutt contain other 
varieties than those described. 
It will be observed that the forms from the remote localities, namely. 
Death Valley and Sevier Lake in the north, Durango and Michoacan 
in the south, and New Mexico in the east, are sculptureless; that is to 
say. are of the smooth surfaced form described bv Frauenfeld. These 
Roswell, New Mexico, examples determined by Dr. Pilsbry extend the 
