286 REPORT ON THE STATE CABINET. 



approach the final disposition of the species of this character in our 

 formations.* 



It would appear that the Genus Strophalosia has been founded upon 

 characters derived from Permian species, in which the interior structure 

 has been well preserved. Of the few European Devonian species of this 

 genus which are cited, I have seen no illustrations of the interior; and 

 these have probably been referred to the genus from the generally similar 

 form, the presence of a nari'ow area, and minute teeth and sockets, which 

 are characters foimd in identical or similar forms in the American strata. 

 It is probable, therefore, that had the interior of these species been 

 observed, they would not have been placed among the Permian Stro- 

 phalosise, but rather among the Producti, to which they seem more 

 nearly allied, t 



It appears to me that we have in the Devonian period the incipient 

 manifestation of the productidian type, which became modified in the 

 later Carboniferous period, where, with conditions favorable to its exces- 

 sive development, it has assumed extravagant forms and proportions, but 

 here and there indicating the characters of its prototype in the presence 

 of an area and foramen, among species of a genus which is characterized 

 by the absence of these features. In the still later Permian period, with 

 changed conditions, we have an approximate return to the earliest forms 

 of the species, or to the prototype ; and in reality the foundation of the 

 genus lies in the Devonian forms which have been referred to Stropha- 

 losia. 



It would appear that the presence, rather than the absence of charac- 

 ters, should be the foundation of generic description and determination ; 

 and in this view Prodd;ctus possesses fewer characters, and, in the absence 

 of hinge-area, teeth and sockets, is less complete than the forms possess- 

 ing these appendages. Nevertheless, the great development of forms 

 and number constituting the Genus Productus during the Carboniferous 



* Those who have the best right to criticise the work, from having themselves labored in a 

 similar field, will appreciate the diificulties to be encountered ; and they will only need to be 

 assured of my earnest intention to dispose of the species \vithout prejudice or partiality to previ- 

 ously expressed opinions. With larger collections before me than I had when originally describing 

 the species under the preceding genera, I have seen cause to modify in some instances the views 

 formerly maintained, and I believe I have shown no leniency towards species proposed by myself 

 on insufBcient materials ; but I am quite unable, at the present time, to reduce the species of this 

 type from these formations, to the limits indicated by European authors who have examined 

 American collections. 



t Prof. De Koninck, in his Recherches siir les Animaux Fossiles, has not recognized the Genus 

 Strophalosia; and the Devonian forms similar to those of our rocks are by him placed under 

 Productus. 



