732 SYSTEMATIC PALEONTOLOGY 



tubes like those which he illustrated, Avhich are found only in the Vincen- 

 town limesand. The specimens which he referred to from 'the friable 

 marls ' which are preserved as ' casts in lignite ' were in all probability 

 representatives of the species T. irregularis. 



" The type of Teredo contorta Gabb, which is preserved in the collection 

 of the Philadelphia Academy of Science, has been carefully compared with 

 the recently collected examples which are here referred to T. irregularis, 

 and there can be no doubt as to their specific identity ; it also is without 

 doubt a Merchantville clay marl specimen, and it is safe to conclude that 

 it is a synonym of T. irregularis:'' Weller, 1907. 



The species is represented in Maryland only by a few fragmentary 

 tubes, the largest of them embedded in a mass of wood from near Post 218 

 on the Chesapeake and Delaware Canal. 



Occurrence. MATAWAN FORMATION. Post 218, Chesapeake and Dela- 

 ware Canal, Delaware ; Ulmstead Point, Anne Arundel County, Maryland. 



Collections. Maryland Geological Survey, Philadelphia Academy of 

 Natural Sciences, New Jersey Geological Survey. 



Outside Distribution. Matawan Formation. Merchantville clay marl, 

 New Jersey. 



TEREDO RHOMBICA n. sp. 



Plate XLV, Pig. 3 



Description. Shell composed of two small plates gaping widely at both 

 extremities, feebly convex and rhombic in outline ; umbones small, 

 rounded, inconspicuous, not overtopping the dorsal margin; anterior 

 dorsal margin horizontal, approximately parallel to the base, slightly pro- 

 duced behind; posterior dorsal margin oblique, diverging from the ante- 

 rior at an angle of not far from 140, merging smoothly into the trun- 

 cated lateral margin; posterior lateral margin obliquely truncate, pro- 

 duced but not lobate at the dorsal extremity; base line straight, less 

 abruptly upcurved behind than in front ; posterior area differentiated by a 

 linear sulcus dropped from the umbones to the posterior ventral margin ; 

 incremental sculpture in front of the diagonal feeble and irregular, 

 behind it sharp and minutely laminar, the dorsal edges free and closely 



