PLATE CXXIV. 
Cyrtoceras citum. 
Page 36. 
Fig. 1. A specimen retaining the test and its ornamentation over the entire exterior of the tube. 
Uppei- Helderbei-g limestone. LeRoy, Genesee county. 
Pig. 2. The internal mould of an individual, showing the revolving furrows of the crenulations, and the 
transverse markings corresj^onding to the foliate expansions of the test. 
Upper Helderberg limestone, Falkirk, Erie co^onty. 
Fig. 3. The retral sinus in the expansions of the test, as shown on the convex or ventral side of a speci¬ 
men. This figure is taken fi-oin a gutta-percha impression of a natural mould and enlarged 
two diameters. 
Upper Helderberg limestone. Cayuga, Ontario, Canada. 
Gyroceras Nereus. 
Page 36. 
Fig. 4. An enlargement to two diameters, of the ornamentation of the test on the ventral side of the tube, 
showing a marked difference in the sinus of the ornamentation from that represented in figui-e 
3 of this plate. 
Corniferous limestone. Cherry Valley, Otsego county. 
Gyroceras laciniosum. 
Page 36. 
Fig. 5. Lateral view of the specimen, showing the curvature of the tube and the transverse ridges corre¬ 
sponding to the ornaments of the test. The matrix preserves the characters and shows the ex¬ 
tent of the fimbria. 
Fig. 6. Id. Outline, showing the transverse section of the tube. 
Corniferous limestone. Chen-ry Valley, Otsego coujity. 
Cyrtoceras Jason. 
Page 36. 
Fig. 7. Lateral view of the internal mould of a large individual, showing the transverse ridges and rows 
of nodes corresponding to the expansions and tubular spines of the test. Several of the trans¬ 
verse lamellffi are seen in the matrix adhering to the dorsal side of the tube. 
Schoharie grit. Clarksville, Albany county. 
