Xylophaga. MOLLUSCA. TEREDINIEvE. 455 



Shell about three quarters of an inch in diameter, with the valves trian- 

 gular, and forming a circular hemisphere when closed together, elegantly 

 striate in various directions, each with a triangular projection in front bend- 

 ing a little inwards; syphons nearly divided to their origin at the junction 

 of the accessorial appendages ; the largest or branchial one has the inside of 

 the orifice fringed with about twenty small tentacula ; foot with a convex 

 extremity ; mouth round ; gullet short, leaning to the left side of the neck ; 

 on the right side of the neck are two large glands ; stomach of two distinct 

 bags communicating at the lower extremity ; the intestine begins close to 

 the termination of the gullet, is small, dilates into a cavity, containing a hard, 

 white globular body of the size of a large pin's head. In the intestine Sir 

 E. Home found a yellow-coloured pulp, which Mr Hatchett, after examina- 

 tion, considered as " vegetable saw dust." 



551. T. nana. — " Valves rounded and without auricles be- 

 hind, a strong conic tooth on the margin above the teeth." 

 Turt. Biv. Brit. 16. t. 2. f. 6, 7-— Drifted wood in Torbay. 

 Diameter about an eighth of an inch ; the conical tooth on the margin of 

 the hinge pointing rather obliquely. 



Gen. CXXXII. XYLOPHAGA— Shell globular, oblique, 

 equivalve, very open anteally, and closed retrally, furnished 

 with accessorial valves about the hinge, which is destitute 

 of long curved teeth under the margin. 



552. X. dorsalis. — -Shell rounded, with a triangular striated 



projection in front of the head of each, and a longitudinal rib 



on the inside. 



Turt. Biv. Brit. 16. and 253, t. ii. f. 4, 5 — Drifted wood, Torbay. 



Less than Teredo navalis ; a mesial groove on the outside, corresponding 

 with the jointed rib on the inside. There is no evidence of its possessing the 

 lengthened calcareous syphons or tube, with their basal appendages, of the 

 Teredo. It is probably nearly related to Gastrochcena. 



Gen. FISTULANA. — Shell equivalve, gaping, with a dorsal 

 plate over the hinge ; tube closed at the inner end. 



1. F. personata. — Valves transversely striated on the retral half; the fine 

 striae on the anteal half regularly and minutely toothed ; dorsal plate thick, 

 four-lobed, with rounded edges — Park. Org. Rem. iii. 202, t. xiv. f. 10. — 

 Teredo antenautae, Sower. Min. Conch, t. cii. — Imbedded in the fossil wood 

 of the London Clay. 



Gen. CLAVAGELLA. — Tube open at the outer end, termi- 

 nating at the inner claviform extremity in tubular pro- 

 cesses ; one of the valves cemented to the tube. 



1. C. coronata Tube elongated, crowned with dichotomously branched 



tubes around a sulcated disk—Sower. Min. Conch, t. cccclxxx— London 

 Clay. 



