MOLLUSCA. 657 



1886. Teredo irregularis Whitf., Pal. N. J., vol. i (Monog. U. 



S. G. $., vol. 9), p. 191, pi. 25, figs. 18-19. 

 1905. Teredo irregularis Johns., Proc. Acad. Nat. Sci. PhiL 



(1905), p. 18. 

 1905. Teredo contorta Johns., Proc. Acad. Nat. Sci. Phil. 



(1905), p. 18. 



Description. Tubes as shown by their casts gregarious, ex- 

 ceedingly tortuous and contorted, sometimes annulated, increas- 

 ing gradually in size from their point of origin, the larger ones 

 reaching a diameter of 10 mm. or more. Shell subglobular, 

 cordate in outline from in front, the beaks a little in front of the 

 middle of the hinge-line, widely gaping behind and open in front; 

 the postero-cardinal extremity somewhat produced in a rounded 

 lobe. Anterior margin rounding from the hinge-line above into 

 the upper margin of the large, deep, subrectangular, antero- 

 basal hiatus which reaches above the mid-height of the shell j 

 basal margin short ; posterior margin obliquely subtruncate below, 

 bent abruptly backward near the hinge-line, and continuing 

 around the postero-cardinal lobe of the shell. Valves ventricose,. 

 the beaks prominent, much elevated above the hinge-line and 

 strongly incurved or enrolled ; the surface curving steeply towards 

 the antero-cardinal extremity and then deflected shortly before 

 reaching the margin, curving less abruptly to the postero-car- 

 dinal extremity. In the casts a very deep and prominent furrow 

 passes from the hinge-line just back of the beaks to the posterior 

 margin just below the post-cardinal lobe of the shell; another 

 faint groove which is less conspicuous upon the larger indi- 

 viduals, crosses the post-umbonal slope in a nearly vertical di- 

 rection from the lower margin of the deep groove already de- 

 scribed behind the beaks to' the posterior extremity of the basal 

 margin ; surface of the anterior half of the shell, as shown in im- 

 pressions of the exterior, marked by exceedingly fine, regular, 

 concentric striae, parallel with the shell margin, 20 or more of 

 which occupy the space of i millimeter. These striae towards the 

 antero-cardinal extremity, are crossed by finer radiating striae, 

 which produce an exceedingly fine reticulate pattern upon the 



42 PAI, 



