MAZATTAN BIVALTES 57 



WTiite or very faintly streaked variety. — Tablet 231 contains 

 4 sp.. regular form, various ages. — 232, 1 sp. flattened, round- 

 ed. — 233, 1 sp. produced ventrallj-. — 234, 1 sp. transTerse, 

 gaping posteriorly. — 235, 1 sp. very transverse. 



Tablets 236 — 241 are arranged to shew traimtions of colour ; 

 but many of tbe specimens are also remarkable for form. — 

 236, 3 sp. vrhite, with very faint brown markings. — 237, 3 sp. 

 brown rays narrow, interrupted. — 238, 2 sp. very narrow and 

 numerous rays. — 239, 3 sp. with broad, sharp rays. — 240, 3 sp. 

 brown predominant. — 241, 3 sp. diffused brown. 



Tablet 242 contains 6 pairs, extremely young, which pro- 

 bably belong to this species. 



Tablet 2i3 contains 2 young valves, which may belong to 

 the transverse white variety. 



84. Teigona humilis, n. s. 



T. t. juniore ovali, umhonihus appressis ; 1 adulta parvd, 

 suhtrirjona, margine ventrali excurvd, lata; vmhonihus non 

 incurvis, parum prominentihus ; Icevi, vel striis incrementi exili- 

 hus : fused, intus on a e til o purpureo dente postico ; 

 dent, lat., antico hrevi, solido, postico longo, exili ; card. 2-3 

 parvis ; lined p)cillii a margine remotd, sinii parvd, suhascen- 

 dente ; Ugamento celato, hrevi ; epidermide tenui. 



This shell might be taken for the young of Dione chiona'a, 

 but for the entire absence of spirally recuiwed umbos ; it differs 

 also from the shells supposed to be the young of T. radiata in 

 the flatness of the umbos and the comparativel.y s;nall size of 

 the teeth. Not being able to affiliate it yvith. any satisfaction. I 

 have been compelled to describe it provisionally. In the 

 youngest stage only the lateral teeth are prominent, and the 

 shape is almost oval ; then the anterior tooth turns roimd and 

 makes a cardinal, and afterwards the other cardinal teeth ap- 

 pear. There seems always a stain of purple inside the ligament. 

 When adult, it becomes subtrigonal, with the dorsal margins 

 rather straight. Neither lunule nor area are defined. 



Theyoimgest specimen measures /ow(/. "02, lat.'Q'ib, alt. '015. 

 The largest „ "ll, „ -16, „ "07. 



Sab — Mazatlan ; rather uncommon, in Spondylus and Chama 

 washings ; L'pool Col. 



Tablet 244 contains 2 pairs united, and 4 pairs of valves of 

 different ages. 



