The Nautilus. 



Vol. III. MARCH, 1890. • No. U. 



ON A NEW SPECIES OF TYLODINA 



BY WM. H. DALL. 



In my Report on the Blake Gasteropods I have (p. 60, pi. xiv, 

 figs. 9, 10) described and figured a shell, which, in the absence of the 

 soft parts, I was obliged to refer doubtfully to the young of Uni- 

 hraculum or Tylodlna, under the head of " JJmbraculum bermudense 

 Morch? " 



This shell now proves to be a genuine Tylodvia, different from the 

 species of the Mediterranean or of California, and which may take 

 the name of T. americana. The shell which was well figured as 

 above, in life has a membranous extension 3-5mm. wide around the 

 margin, continuous with the epidermis. The latter is smooth and 

 pale with radiating broad purplish rays of color. The animal 

 is much smaller than that of T. Rafinesqui in proportion to the shell, 

 which abundantly covers it, and it emits a dark purple dye. It 

 does not seem to differ essentially in the superficial characters of its 

 soft parts from the species of the Mediterranean, which, however, has 

 not been very well figured. The gill is attached to the edge of 

 mantle on the right side. The other characters are much as stated 

 in H. & A. Adams' generic description of the genus (Gen. Rec. 

 Moll. II, 42). 



The Blake specimen was obtained off Havana, dead, in 80 fathoms. 

 The present specimen was obtained on the northern border of the 

 Gulf of Mexico by the U. S. Fish Commission at Station 2406, in 26 

 fathoms, coarse sand and broken coral, on the line between the 

 mouth of the Mississippi River and Cedar Keys, Florida. 



