ra kOHYDBB ' gg 



T - OOTH1CUI <'|-. IM. If), figs. 28, 29. 



The Origioal desrription will I,,- found ,,n ,,. 71, vol. xiv 

 The type of this little shell was collected at ( iatalina Mand l, v f > r 

 roper. It ,s an exceptionally elevated species, the dorsal ridge 

 being acute, and t he an-le <.f divergence about 80. The type (Mm 

 Smiths, In,t. 16271) having been glued to a glass tablet formerly' 

 not m very good condition, but < -Center's excellent description 

 the figures Lore given (representing the half of a median valve 

 and a profile of the tail valve), will readily identify it. 



T. RUBER L. PI. 15, fig. 25 (girdle-scales, x 125). 



T. DENTIENS Gld. PI. 15, fig. 26 (girdle scales, x 250.) 



Subgenus SPONGIORADSIA Pilsbry, 1894 (n. s.-g.) 

 Trachyradsia CPR. in part, exclusive of its type Ch. fulgetrum 

 Valves smoothish, having two or several side slits, and extremely 

 >gy eaves and sinus, the latter squared. Girdle sparsely beset with 

 minute elongated scales. Type Tr. aleutica. 



It is somewhat doubtful whether this group should rank under 

 Callocaiton or Trachydermon ; but as the girdle, sinus and gills more 

 eemble the latter, I have placed it here. The spongy eaves and 

 Isioid valves resemble Trachyradsia (plus Stereochiton), but the 

 m that group, as in typical Callochiton^ bridged by a lamina 

 ding across from one sutural lamina to the other. 

 Hut two species are known to belong here : aleutica Ball and miilti- 

 dentata Cpr. 



T. ALKUTICA Ball. PI. 15, figs. 30, 31, 32, 33. 

 The original description is given on p. 84, vol. xiv. 

 This is a small, dull purplish-red species, much elevated but 

 ounded at the ridge, valves broadly v-shaped, the anterior border 

 h being concave, the lateral areas a trifle raised but 

 indistinct, whole surface obsoletely punetulated l.y the comparatively 

 large megalaesthetes, and showing some lines of growth. 



The most prominent characters are presented by the interior of 

 the valves, which are flesh-colored, rather thick, and have the pos- 

 Jnor border of the tegmentum broadly reflexed. The wide eaves 

 are coarsely and densely spongy, the teeth bem- reduced to very 

 slight prominences or wholly obsolete on some valves; but the num. 

 ber of punctate slit-rays shows that the side-slits if developed would 

 o 



