Mr. SowERBY on the Spiral Tubes in the Terebrahtla. !xl5 



Fig. 1. Terehratula striata, Anomia striata of Martyn*. The lower 

 valve containing the spiral tubes considerably enlarged, 

 the specimen being little more than one inch long. 

 a. a. Sections of those parts of the spiral tubes by which, 

 they are attached to the upper valve. 

 h. The place of the triangular aperture immediately 

 above the lower beak. 

 Fig. 2. Terehratula striata. The two valves with one end cut oft'. 

 a. The triangular aperture between the beaks. 

 h. Section of the spiral tube near the end. 

 I suspect Anomia cuspidata-\-, Linn. Trans, vol. iv. PI. 4, with 

 the beak of the perforated valve lengthened and reverse, may 

 have a similar construction within, as well as Anomia subconica of 

 Martyn, tab. 47- _ 



Since I presented to the Society a sketch of an Anomia or Te- 

 rebratula with a spiral internal cartilage, J. have received a species 

 of Terehratula of a very different construction with a spiral carti- 

 lage ; and I conceive that a figure of this species would be a con- 

 venient addition to my former communication, as showing that 

 the spiral cartilage is less confined to shells of a certain external 

 form than might have been expected. Such as I had seen before 

 had straight elongated hinges, and the deeper shell had a trian- 

 gular foramen, or distant curved beaks indicating it. The present 

 sketch (fig. 3, 4.) represents a shell curved laterally from the 

 hinge, which must be very short, the beaks very small, and with- 

 out any space for a triangular foramen externally, although within 



* Mr. Martyn sent me this specimen some years since. It shows the triangular aper- 

 ture, although his figure does not j but the shell showed no sign of the tube till I broke it 

 for information. 



t Figured, since the reading of this Paper, as Spirifer cuspidata in Mineral Concho- 

 Ingy, tab. 120. 



VOL. XII. 3 X thtrc 



