MAZATLAN BIVALVES As) 
young as much as in the adult shells. A very small specimen was 
found to contain a minute young one. Specimens as broad as 
"Zin. are very uncommon. One specimen was found having its 
siphon pipe projecting nearly half the breadth beyond the shell. 
Smallest specimen measures cong. ‘02, lat. °03 alt. °O15. 
HKlongated +) +9 bE) Us ’ 99 1, 33 "02. 
Oval 59 23 99 ‘2s 99 "26, 33 14. 
Largest by 7 ie aL Ssnee yh iictlye mana te Ag 
Hab.—Mazatlan: inhabitme the burrows of worms and Mol- 
lusks in Chame and Spondylus Lamarclai; also in dead Balani 
on Strombus galea; not uncommon; L’pool & Havre Coll. 
Tablet 80 contains 22 valves and 1 pair, jun. of various 
shapes.—8l, a pair of regular shape with young nullipore grow- 
ing on; pair with long siphon pipe; valve with internal lamina : 
5 broken valves shewing hinge structure, &¢.—82, the largest 
specimen, from hole of Lithodomus caudigerus in Strombus 
galea; a Balanus with oval Spheenia taken from within. 
. 
We insert here a notice of a unique sheli deseribed by A. 
Adams in the An. Nat. Hist. 1854, p. 418, under the name of 
Tyleria fragilis. Though named in honour of Mr. Tyler, he had 
it in his possession a considerable time without knowing of any 
thing remarkable attending it. I have taken several journeys 
to Liverpool and made enquiries in London, in hopes of seeing 
it, without success: but, as evidence that it is not mythical, I 
deposit, on Tablet 83, drawings made by Mr. Sowerby and 
most kindly placed at my disposal by H. Adams, Esq. It 
is possible that it is a deformed shell. I have occasion- 
ally noticed valves of Sph. fragilis with a tendency towards 
the same crenation at the posterior end, apparently through 
irritation of sand, &c.; also with the pallial line broken up. 
Mr. Tyler states that he found it in a burrow in the large 
Spondylus from Mazatlan; L’pool Col. 
Aug. 1855. d 
