TECTURA. 269 



Tectura alveus. 



Fig. 13. 



Shell oblong-oval, compressed at the sides, thin, colored with a network of 

 white and brown. 



Patella nlveus, Coxrad, Joiirn. Acad. Nat. Sc. vi. 267, pi. 11, fig. 20 (1831). 



Patdloidea alveu^, Couthouv, Bust. Jouni. Nat. Hist. ii. 177. — De Kxy, N. Y. Moll. 



162, pi. 9, fiig. 194. 

 Lottin alreiis, Gould, Inv. 1st ed. 154, fig. 13. 

 Tertura ulceus, yxiMPSON, Check Lists, 4. 



Shell small, thin, and fragile, elevated, compressed at the sides, 

 so that the margins are nearly parallel, the ends of equal 

 breadth, and obtusely rounded ; apex at the posterior 

 third, pointing forwards ; outer surface beautifully 

 checked with the lines of growth, and fine, but dis- 

 tinct, radiating lines ; color a reddish brown, with oval 

 or circular yellowish white spots, arranged in a some- 

 what regular manner, so that the whole resembles a net- 

 work. The thinness of the shell allows the external 

 coloring to appear on the inside ; edge entire. Length, five tenths 

 of an inch ; breadth, three tenths of an inch. 



Found abundantly on the eel-grass QZostera marinci)^ to whose 

 narrow leaves its form is exactly adapted. Whole coast of New Eng- 

 land ( Stimpson) . 



In old specimens a lateral compression is very obvious, and the 

 sides are at least parallel, and sometimes incurved for one half the 

 length of the shell. The apex, when not worn off, is acute, and 

 projects distinctly forwards. The markings usually give the shell a 

 checkered appearance ; but occasionally we have stripes, as in the 

 preceding species. 



This shell is the very miniature of Patella compressa. Mr. Sow- 

 erby suggests that it bears the same relation to P. testudinalis as 

 Patella compressa does to P. miniata; in other words, it is the same 

 species, changed in form from having adhered to a narrow sea-weed 

 instead of a stone. The general marking of the shell, and the cir- 

 cumstance of its seldom, if ever, being noticed living anywhere ex- 

 cept upon the narrow leaves before mentioned, render this opinion 

 not at all improbable. 



