1 194 TRTRAIT.ODON 



LAMPHORHAMPHUS. 



Male and female shells alike; dull-colored; beak sculpture 

 nearly or quite radial, marsupium occupying the entire inner 

 branchiae, forming a pad-like mass. 



Genus TETRAPLODON Spix, 1827. 



Castalia Lamarck, An. sans Vert., VI, 1819, p. 66. 

 Tctraplodon Spix, Test. Fluv. Bras., 1827, p. 32. 

 Prisodon Lka, Synopsis, 1852, p. 18. 



Shell triangular, solid, inflated, with a high, sharp posterior 

 ridge, behind which it is decidedly truncated ; beaks very full 

 and high, sculpture strictly radial, or with one or two pairs of 

 the central bars coalescing below, the whole extending more or 

 less over the disk as strong ridges ; epidemiis thick, dark, dull- 

 colored ; hinge line arched ; there is a very strong, compressed 

 pseudocardinal in the left valve, and there are two in the right, 

 all in front of the beaks ; behind them are several denticles ; 

 one lateral in the right valve and two in the left; all the teeth 

 strongly vertically ridged ; beak cavities deep, not compressed ; 

 anterior muscle scars small, deep ; nacre whitish. 



Animal having the labial palpi wider than long; margins of 

 mantle inferiorly open, but united posteriorly to form two 

 -siphons, branchial and anal ; branchial opening surrounded with 

 papillae ; anal opening smooth ; outer branchia? united to the 

 mantle to their posterior ends; inner united to the abdominal 

 sac; foot tongue-shaped, thick, produced anteriorly. (Tro- 

 schel.) 



Type. Tctraplodon pcctinatum Spix. 



A very natural, small group of South American Unionidae. 

 The shells are generally triangular with high beaks having 

 radical sculpture, which extends well on to the disk and in 

 some cases all over it. The teeth are usually strongly vertical- 

 ly sculptured, the pseudocardinals are often somewhat split up. 



