JAN. 19, 1921 PRICE: SHELL REGENERATION IN A BRACHIOPOD 



33 



I . Description of abnormal sculpture. — The area of abnormal sculp- 

 ture extends from the front margin inward, beyond the center of the 

 shell, for about three-fifths the height and is lobate in outline. It is 

 expanded in the central region where it is sharply defined and has a 

 semicircular border. The lateral borders are somewhat irregular and 

 abnormal sculptural elements (costae) are superimposed upon 

 the normal sculpture in these regions. 



The megascopic sculpture 

 of the abnormal area con- 

 sists of two elements. 

 Radiating costae of normal 

 size extend inward from the 

 front margin where they 

 are parallel to each other 

 and are rather evenly 

 spaced at the normal in- 

 terval for this portion of 

 the shell. Slight irregu- 

 larities in spacing appear. 

 Fig. 1. Impression of the interior of a pedicle The costae diverge inward, 



valve of Derbya crassa (X P/s) showing an area of the divergence being ac- 

 abnormal sculpture. From the collection of West cglgj-ated in amOUnt bcVOUd 

 A'irginia Geological vSurvey, locality 203. i r- i i • " ,* 



the nrst undulation oi 

 growth. They increase irregularly in number toward the central 

 region of the shell by the interpolation of smaller costae in such a 

 manner as to produce a fasciculate distribution. Both the fasciculate 

 design and the irregularity of the interpolation are abnormal in this 

 species. 



The undulations of growth of the normal portion of the shell which 

 intersect the abnormal lobe are continued with unequal distinctness 

 across it. 



Faint transverse lines, sharply convex toward the back, cross the 

 costae at three points, each originating just beyond one of the growth 

 undulations of the normal portion of the shell. They appear to be 

 weak undulations of growth. 



The minute granular projections which covered the interior sur- 

 face of the shell were finer upon the abnormal area than upon the nor- 

 mal shell. 



The abnormal lobe has the appearance of a patch placed over a 

 hole of somewhat irregular outline and slightly overlapping the edges 



