MOLLUSCS. 



279 



\- 



__il 



Mnliiiia laterals 



ri/relinUles 



many otluT fcii-ins. Mdvtni solidissiiKa occasionally n^achos a U'nyth of over six inclies, 

 lias the cardinal teeth delicate, and has a shallow pallial sinus. J/, oixdis hut rarelv 

 exceeds four inches in lenjith, and has the teeth short and 

 the sinus deej). Separated from Mavtra jiroper by an annu- 

 hir pallial sinus is the sub-genus Jfulhiid, of which one spe- 

 cies, Jlulinia hileniHs, occurs nearly the whole !eM;_;tli of our 

 eastern coast. 



liangia (also known as Giidtliodoii) is a brackish-water 

 genus, represented in tiie soutliern United States by tiie spe- 

 cies R. cyrcnoides. In the gulf states this sjH'cies occurs in vast numbers. Baid<s of 



dead shells, tliree or fom- feet in tliick- 

 ness, occur in many places, sonu! of 

 Ihcm twenty miles inland. The city 

 (.f .Mobile is built on one of these 

 banks, while the road over which the 

 inliabitants of New Orleans travel in 

 order to reach Lake I'ontchartrain " is 

 made of these shells, procured from 

 the east end of the lake, where there 

 is a mound of tiiem a mile long, fifteen 

 feet high, aiul from twenty to sixty 

 yards wide; in some placesit is twenty 

 feet above the level of the lake." 

 The family 'i'i:i.i,i:xii).i<: vies with the \'eneridie in its beautifully-colored species. 

 Like the members of that family, they are mostly iidiabitants of tlie warnu'r seas of the 

 world, the small number of species which stray into tlie more nortliern waters 

 being dull colored, and far less attractive than their tropical relatives. The shells are 

 long, compressed, anil usually closed and equi-valvc ; and one marked feature that i.s 

 generally found is tliat the half of the shell in front of the umbones is longer than that 

 behind them. The cardinal teeth are at most two in number; the lateral teeth are oc- 

 casionally obsolete. The hinge ligament is usually exteriud and posterior. The mantle 

 is widely open in front, and the two very long arul slender si])honal tubi's are com- 

 pletely separated. The foot is triangular and compresse<l. In most s])ecies the shell 

 is very dense, and highly ))olished, and not infrequently is white, enlivened by bands 

 or stripes of delicate shades of red or yellow, while in others the effect is heightened 

 by the finely sculptured lines. 



In TelHna, which readies its highest development in the Iinlian Oi'can, the shell is 

 rounded in front and angular posteriorly, a fold running from the angle to the ninbo. 

 The siphons are very long, and can be extended to at least twice the length of the 

 shell, and, as a necessary sequence of such extensibility, the 

 and deep. In Strlgilla the surface is ornamented with 

 divaricating lines, like those of Ct/clit.':, descrilied on a pre- 

 ceding page. 



Our nortliern forms belonging to this family are dull 

 colored .and unattractive. Tellina tenera, which occurs from 

 Florid.a to the Gulf of St. Lawrence, is an exception, for the 



delicate rose-color which tinges the otherwise white shell makes it an obji-ct of 

 beautv. The siphons are verv long, several times the length of the l)od\-, and hence 



