TECTURA. 269 



Tectura alveus. 



Fig. 13. 



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

 white and brown. 



Patella nli-eus, Conrad, Journ. Acad. Nat. Sc. vi. 267, pi. 11, fig. 20 (1831). 



PattUoidea alvem, Couthouy, Bost. Journ. Nat. Hist. ii. 177. — Db Kay, N. Y. Moll. 



162, pi. 9, fig. 194. 

 Lottin alreus, Gould, Inv. 1st cd. 154, fig. 13. 

 Tectum alreus, Stimpson, Check Lists, 4. 



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



so that the maro-ins are nearly jmrallel, 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 reirular manner, so that the whole resemldes a net- >^^ 



■^ ' . T. alveus. 



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 {Zostcra marina'), 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 comprcssa. Mr. Sow- 

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

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

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

 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. 



