GASTROCHiENA. 131 



28. PLiCATlLis, f. 3, Deshayes. — Parviuscula tenuis recta, 

 area postica conspicue sulcata, margiue dorsali recto, margine 

 ventrali paulo convexo. — Smaller than 0. rostrata and much 

 less tortuous in the outlines, but strongly plaited on the 

 posterior area. 



29. MTTiLOiDES, f. 8, Lamavck. — G. rostratce similis sed 

 laevigata, latere antico ante umbones producto, subacuminato; 

 latere postico ante carinam profunde depresso; margine 

 ventrali magis conspicue convexo. 



Genus FISTULANA. 

 Plate 471, f. 15, 16, 17. 



Molluscum vermiforme arenicolum, tubam rectam clavatam 

 ad terminum anticum clausam, ad terminum posticum 

 divisam formanti. Valvss rectse, postice elongatoe, antice 

 brevissimae, utrinque truncatae. — The valves are long and 

 somewhat straight, with very short anterior sides, and the 

 tubes are long, club-shaped, divided like those of Teredo at 

 the narrow posterior end, and closed at the broader anterior 

 end, where the valves are found. The Fistulanae burrow in 

 sand. 



Species, 



1, clava, f. 15, Lamarck. — Valvae quadratim elongataa 

 utrinque truncate, rectae ; hiatu arcuato ; area antica bre- 

 vissima pectinata. Tuba laevigata. — Valves elongated, 

 straight, truncated at each end ; hiatus arched, anterior side 

 very short, pectinated. Tube smooth. 



2. agglutinans, f. 17, Deshayes. — Valvae G. clavce similes 

 sed magis angustae ; hiatu angulato. Tuba agglutinans, 

 lapillis aveuseque granis ornuta. — The valves are like those 



