MOLLUSCA. 657 



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



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

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



(i90S),p. 18. 

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



(1905), p. 18. 



Description. -^Tuhes 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 oi 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; 

 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, 201 or more of 

 which occupy the space of i millimeter. These stria; towards the 

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

 which produce an exceedingly fine reticulate pattern upon the 



42 PAL, 



