264 UNITED STATES GEOLOGICAL SURVEY OF TOE TERRITORIES. 



Teredo globosa, M. & H. 



Plate 30, tig. 13 (burrows). 

 Teredo globosa, Meek and Hayden (1858), Proceed. Acad. Nat. Sci. Pliilad., X, 53. 



Fig. 31. Fig. 32. Shell globose-cordate, thin ; posterior side rounded 



'•. f ~'\ or subtruncated, and nol very widely gaping; anterior 

 \>4 «- 4<Jf -^ hiatus large, rectangular, extending from the middle of the 



j,i W lit. 1¥ ° ' ° 



\0? base half-way up the valves; dorsum rounding poste- 

 Teredo globosa, M. & H.* riorly ; umbonal region gibbous; beaks distinctly in- 

 Fi g . 3i. Posterior view, curved oblk ] forward, located in advance, of the 



magnified three di- l J 



ameters. middle. Surface ornamented by concentric lines, which 



Fig. 32. Left side view in n i n 



of same, magnified tollow the curves and angular flexures ot the tree border, 

 m same way. an( j are crossec | hy an obscure, small groove, descend- 



ing from the beaks. 



Length, 0.23 inch ; height, 0.24 inch ; convexity, 0.22 inch. 



The parts of the ventral borders of the valves which come in contact 

 beneath are comparatively narrow and prolonged downward ; being that por- 

 tion of the base between the anterior angular hiatus and the much smaller 

 oval aperture formed by the gaping of the valves behind. I have not been 

 able to determine very exactly the nature of the vertical groove descending 

 from the beaks. On internal casts, it is small, and passes from the beaks 

 to the corner of the anterior notch, thence down near its vertical margin 

 to the base. Some little distance back of this groove (on the cast), there is 

 sometimes a single, raised, thread-like line extending from the beaks nearly 

 straight down to the base. Between this line and the groove, there is a 

 narrow band-like space, passing down from the beaks, which is a little more 

 elevated and rougher than other parts of the cast. 



Our specimens are not in a condition to show very clearly the details of 

 the surface-markings ; but the concentric lines can be seen, as usual, to be 

 coarser and less regular on the posterior side; and, under a good lens, they 

 are seen, where deflected upward parallel to the margin of the anterior hiatus, 

 to be fine, regular, and minutely crenulate. 



The tubes (see pi. 30, fig. 13) are generally nearly straight and parallel, 



* Figures of the shell of this species having been inadvertently omitted in making up the plates, 

 the above cuts of the same are introduced here to aid in its identification. 



