NUDIBRANCHIATA. 225 



Found by Professor Adams in mud dredged up from New Bed- 

 ford Harbor. Connecticut (^Linsle/j). 



This is the smallest species hitherto described, but it bears every 

 mark of maturity. It has a general resemblance to the T. turnatilis, 

 of Europe, but the spire is shorter and less acutely pointed. The 

 punctured revolving lines, which cover the anterior half of the lower 

 whorl, are constant and decisive marks of distinction, in addition to 

 its minute size. 



Order NUDIBRANCHIATA.* 



Gills exposed, or contractile into cavities on the surface of the 

 mantle. Adult animal without any shell. Larva sliell-bcaring. 

 Foot elongate, formed for walking. Sexes united. 



While the numerous tril3cs of Mollusks furnished with testaceous 

 coverings offer us objects of contemplation, rcmarkalilc alike for 

 their extreme beauty and the durability of their calcareous envel- 

 opes, the scarcely less extensive and certainly far less known fami- 

 lies of Naked-gilled Gasteropods exhibit an astonishing variety of 

 form, extreme delicacy of organization, and great diversity of color, 

 to captivate the eye and occupy the attention of those who wander 

 by the shore or explore the depths of ocean. Clinging to the stems 

 of floating sea-weeds, many, like the Anthobranchs, will be seen 

 extruding their flower-like gills of surpassing elegance, exploring 

 with their foliated tentacles or complex mantle-filaments the plants 

 around them, the brilliant hues of their striped or spotted bodies 

 glancing through the water ; some will be observed with bodies so 

 fragile and pellucid that you may see the color of their blood and 

 count the pulsations of their hearts ; some will be seen to have their 

 gills disposed in rows of papillary tubercles on the sides of their 

 bodies, like the JEo/ids, or tree-like, and branching, like the Trito- 

 nias ; the foreheads of some will be smooth and simple, while those 

 of others will be found adorned with various singular appendages ; 

 in others, again, all processes will disappear, all branchial arrange- 

 ments vanish, and we shall meet with forms almost as simple in 



* The manuscript of the Xndihranckiafa was left by Dr. Gould quite ready for the press. 

 I have inserted a few additional references to American authors, and descriptions of fam- 

 ilies from the " Genera of Recent Mollusca." 



The original drawings from which the figures in the plates were copied have also passed 

 through Dr. Gould's hands, and were selected by him for engraving. I am responsible 

 only for the grou])ing of the figures. — W. G. B. 

 15 



