316 
PALAEONTOLOGY OF NEW YORK. 
ably attached to some extraneous body, a phenomenon which has been noticed 
in Productus (P. compledens and other species). In some of the earlier species 
of this genus, e.g., S. radicans, Winchell, of the Hamilton group, S. scintilla, 
Beecher, of the Choteau limestone, and S. Keokuk, Beecher, of the Keokuk 
group, the entire shell is small, and the pedicle-valve attached by almost its 
entire surface; the spines on these valves are all attached, creeping like root¬ 
lets in irregular, flexuose lines over the surface of the host. A Permian form 
similar to these was described by Professor King,* under the name S. parva, 
which may be the young of some of the larger associated species; but the 
Hamilton and Lower Carboniferous forms can not, with our present knowledge, 
be regarded as undeveloped shells. The affinities of Strophalosia with both 
Chonetes and Aulosteges, serve to make the transition from the chonetoid 
shells to Productus a complete and very easy one. 
No satisfactory subdivision of the species of Strophalosia has been made. 
Dr. Waagen described a number of new species from the Productus limestone 
of India, and proposed a grouping therefor upon the basis of the general form 
of the shell. It may be suggested that a good basis for a provisional subdivi¬ 
sion of the genus can be found in the character of the external surface of the 
brachial valve. This valve is spiniferous, as in S. excavata , Geinitz, and the 
majority of the species; lamellose, or covered with concentric lamellae or 
varices of growth, as in S. lamellosa, Geinitz; or smooth, as in S. Leplayi, Geinitz, 
S. plicosa, Waagen, 8. radicans, Winchell, etc. 
In American faunas Strophalosia is of rare occurrence. The following- 
species only may be safely referred to the genus: Producta truncata, Hall, of the 
Marcellus and Hamilton faunas; Chonetes muricatus, and Productella hystricula, 
Hall, of the Chemung group; Crania radicans, Winchell, from the Hamilton 
group ; 8. numularis, Winchell, of the Marshall group; S. scintilla, Beecher, of the 
Choteau limestone; S. Keokuk, Beecher, from the Keokuk group, and probably 
Aulosteges spondyliformis, White and St. John, from the Coal Measures. To 
these may be added 8. Rockfordensis, sp. nov., from the Upper Devonian of 
Iowa. None of these species, however, show the typical development of the 
interior found in the Permian forms. 
* Monograph of the Permian Fossils of England, p. 102, pi. xii, fig. 33. 
