316 PALEONTOLOGY OF NEW YORK. 



ably attached to some extraneous body, a phenomenon which has been noticed 

 in Prodoctus (P. complectens 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, tlexuose 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 l)e 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 lamelloe or 

 varices of growth, as in S. lamellosa, Geinitz; or smooth, as in S. Leplayi, Geinitz, 

 jS. plicosa, Waagen, iS'. 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 ; S. 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 S. Rockfordensis, sp. nov., from the Upper Devonian of 

 Iowa. None of these species, however, show tlie typical development of the 

 interior found in the Permian forms. 



♦ Monograph of the Pei-inian Fossils of England, p. 102, pi. xii, fig. 33. 



