278 CRETACEOUS PELECYPODA 



15. Astarte, Sower by, 1817, fCrassina, Lam., 1818). Shell sub-trigonal 

 or sub-orbicular, witb attenuated, pointed, approached beaks ; surface concentrically 

 striated or laminated, hinge with three cardinal teeth in each valve ; in the right 

 the anterior and posterior are very small ; in the left valve the median and 

 sometimes posterior are large, and the anterior is sometimes only indicated, as 

 well as a lateral tooth, situated just above the muscular impression ; ligament 

 long, generally lodged in a depression and supported by fulcra ; muscular impres- 

 sions rounded, or ovate, deep ; internal margin of shell smooth or crenulated. 



The first authentic specimens of Astarte appear with the mesozoic period 

 and continue up to the present time, being mostly found in northern seas. 



Mr. Conrad (Am. Journ. Conch., v, p. 46,) suggests that Sowerby's oolitic 

 ^ type species Astarte lurida is generically distinct from the recent northern forms 

 which Lamarck called Crassina. I have compared this type species also with 

 recent Astarte, and I find that in some of the more oval species there is also a 

 thickening of the anterior lunular margin in the right valve, as noted in the 

 fossil lurida. I do not think that they could be on that account generically 

 separated, though I admit that there are probably several other genera represented 

 among the fossil species which we call Astarte; I would particularly allude to 

 Eriphyla, Orotriania, and Myrtea, a sub-genus of LuGvna, Very closely allied to 

 the last, if not identically the same, is Conrad's Lirodiscus. 



15 a. Gonilia, Stol., 1870. Shell orbicular, small, hinge with three distinct 

 cardinal teeth in each valve, surface with angular striae, no epidermis ; type, 

 Lucina? (or Astarte) bipartita, Philippi, (Abbild. and Besch. Conch., vol. ii, 

 Astarte, pi. 1, fig. 9; non A, Upartita, Sow.). The round, rather Lucinoid form 

 and the angular striation of the surface indicates in this species a distinct 

 section of Astarte, similar to Cyclas, a sub-gen. of Lucina, 

 -p 16. Grotriania, Speyer, 1860, (Zeitsch. d. deutsch. Geol. Gesellsch., vol. xii, 



p. 496). Shell roundish, moderately compressed, concentrically sulcated or striated, 

 lunula and area very deeply excavated ; beaks produced and pointed, hinge with 

 two or more (often three) cardinal teeth in the right and two in the left valve, 

 the middle tooth in the former and the anterior in the latter being the strono'est ; 

 each valve with a rib-like margin^ lateral tooth on either side, accompanied by 

 a groove, muscular impressions oval, moderately excavated, internal margin finely 

 crenated. Type, Grot, semicostata, Speyer, from the oligoc^ne beds of Soellino'en. 

 One species also occurs in the South Indian cretaceous rocks. 



This genus greatly resembles in external form an Astarte, but is readily 

 distinguished from it by the presence of the peculiarly elongated lateral teeth and 

 the deep lunula and area. The cardinal teeth equally easily distinguish the genus 

 from Uriphy la, Gabb, (bosiniin^J, in which the pallial line is truncate posteriorly, 

 or more or less distinctly sinuated. 



17. FrcBGonia, Stol., 1870. Oval, elongated, solid, very inequilateral, beaks 

 sub-anterior, approached, incurved, surface concentrically lamellated or striated ; 

 muscular impressions strong; hinge with two cardinal teeth in the left and three 



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