UNGULINID^. 215 



Tancredia, Lycett, 1850. 



Etym. — Dedicated to Sir Thomas Tancred, Bart., founder of 

 the Cotteswold Naturalists' Club. 



Syn. — Hettangia, Terquem. Palseomya, Zitt. and Goub., 1861 



Distr. — Fossil, 12 sp. Lias — Bath Oolite; Britain, France. 

 T. Dionxillensis^ cxix, 65). 2\ curtansata^ M. and L. (cxix, 66). 

 T. {Palseomya) Deshayesii (cxix, 64). 



Shell trigonal, smooth; anterior side usually longest; cardinal 

 teeth 2"2, one of them small; a posterior lateral tooth in each 

 valve ; ligament external ; muscular impressions oval ; pallial 

 line simple. 



This genus is closelj' related to Meekia of Gabb, Cretaceous, 

 California, but difters in being-closed instead of gaping anteriorly', 

 as well as in wanting the peculiar anterior angularity of that 

 type ; which also presents some differences in the nature of its 

 hinge-plate, and is said to have its ligament subexternal instead 

 of decidedly external. 



Meekia, Gabb, 1864. 



Distr. — 3 sp. M. radiata, Gabb (cxix, 61). Cretaceous ; 

 California. 



Shell oblong, subinequilateral, posteriorly rounded, anteriorly 

 somewhat produced and turned upwards hook-like, terminating 

 in a point ; surface marked with striae of growth only ; hinge 

 with two robust, triangular teeth on the right valve, and one 

 large and one small one on the opposite side, the large one being 

 received between the two of the right valve ; posteriorly on each 

 side is an indistinct lateral tooth. A short robust plate separates 

 the anterior muscular scar from the cavity of the beak. 



Family UNGULINID^. 



Shell suborbicular, closed, sometimes a little irregular; hinge 

 composed of two bifid, divergent cardinal teeth, and no laterals; 

 ligament marginal, mantle-margins united, with pedal and anal 

 openings ; foot vermiform. 



IJngulina, Daudin. 



Etym. — Ungidina^ like a hoof. 



Syn. — Clotho, Basterot, non Faujas. 



Distr. — 4 sp. Senegal, Philippines, excavating winding gal- 

 leries in coral. ? Carboniferous, Miocene. U. ohlonga^ Daud. 

 (cxix, 68). 



Shell suborbicular ; ligament very short ; epidermis thick, 

 wrinkled, sometimes black; hinge-teeth 2-2; muscular impres- 

 sions long, rugose. 



Animal with the mantle open below, fringed ; siphonal orifice 

 single ; foot vermiform, thickened at the end and perforated, 



