256 GINGLYMACONCHA. PHOLEOBIAD. 
Synopsis Generum. 
Stirps 1. Testee infra anticé late emar- 
ginate. Cardo edentulus ........ 6. GASTROCHENA. 
Stirps 2. Testee integree. Cardo eden- 
GUMS) <a vce ce ee, oes 2 es tema cle ee rrr 
Cardo in utraque valva dente obtusius- 
cil Mme Ire crac. 
Genus 6. GASTROCHAENA. 
Gastrochena, Spengler, Cuvier, Lamarck. 
The shells equivalve, ovate, truncated below anteriorly and 
gaping, closed behind ; the umbones nearly terminal, anterior 
simple ; the ligament external ; the hinge without teeth ; the 
valves connected to each other behind the ligament by a mem- 
brane. The respiratory tubes are very long, rounded, connected, 
their extremities cirrated. 
The Gastrochrene inhabit the sea ; they perforate shells and 
limestone rocks, lining their perforations with testaceous matter, 
which is often produced beyond the perforations, covering half 
of their respiratory tubes. 
GASTROCHZNA MODIOLINA. Tab. III. fig. 3. 
Shell light brown, fragile, thin, opaque, smooth, concentri- 
cally striated. Length of the shell one inch; height an inch 
and a half. 
Mya dubia, Penn. Brit. Zool. iv. 82. t. xliv.; M. §& R. Trans. 
Linn. Soc. vin. 33; Turt. Conch. Dict. 104. 
Pholas Faba, Pult. Cat. Dorset. 27. 
Pholas pusilla, Poli, Test. 1. 50. t. vil. f. 12, 13. 
Mya pholadia, Mont. Test. Brit. 28; Flem. Edinb. Encycl. 
vil. 87. 
Mytilus ambiguus, Dill. Desc. Cat. 304. 
Gastrochzena modiolina, Lam. Hist. Nat. des Anim. sans Vert. 
v. 447. 
Animal whitish, the fringes of the tubes of respiration brown, 
inclining to purple. 
