210 C. E. Beecher — A 7 . A. Species of Strophalosia. 



form and surface ornamentation. The more important internal 

 characters, such as the cardinal muscular lamellae, small dorsal 

 adductor scars, spiral impressions, attached ventral valve, and 

 cleft dorsal callosity, are incompatible with that genus as ex- 

 pressed by the species Leptaena transversalis Dalman, 



The muscular scars and hinge characters are similar to the 

 strophomenoid group, but on the other hand, the Productidte 

 possess many elements which find an expression in Lejttcenisca, 

 and it is evidently genetically related to that family and may 

 be considered as an ancestral form of Strophalosia. 



With this view, the spiral markings on the interior of the 

 dorsal valve represent the common reniform impressions of 

 the Productidse, and not true brachial impressions, such as 

 occur in Koninckina. Compare figure 5 with typical Stroph- 

 alosia represented in figures 6 and 16. 



Tale University Museum, May 1st, 1890. 



Art. XXXIII. — North American Species of Strophalosia / 

 by Charles E. Beecher, Ph.D. (With Plate IX). 



The little shells described in this paper from Carboniferous 

 and Devonian formations of North America are always found 

 attached to some other organism, and none have yet been 

 noted which reach the size and spinoseness of their Permian 

 congeners. They were evidently derived from free ancestral 

 forms, as they all exhibit a pedicle-sheath, although from their 

 habit of fixation a pedicle would be functionally useless. It is 

 natural to suppose, however, that in their extremely early 

 stages, the shells were unattached, and simply anchored by a 

 pedicle, as in ordinary brachiopods, and after a brief free ex- 

 istence, they fixed themselves to some foreign object by their 

 tubular spines, and by calcareous cementation of the ventral 

 valve. In many cases the specimens are found gregarious, as 

 many as twelve having been seen on the shell of a single gas- 

 tropod, which itself was commensal with a crinoid (see fig. 24). 



The first specimens discovered by the writer were found 

 upon individuals of Platyceras equilaterale Hall ; among some 

 collections made by Professor F. H. Bradley and Rev. D. A. 

 Bassett, from the Keokuk shales, at Crawfordsville, Indiana. 



Subsequent search resulted in determining that the species 

 described as Crania radicans Winchell, belonged to the genus 

 Strophalosia. Soon after this, Mr. Charles Schuchert kindly 

 called my attention to a third and minute species, which he 

 had discovered among some specimens of larger brachiopods, 

 collected by Mr. R. R. Rowley from the Choteau limestone of 



