226 PLEUROBRANCH^A. 



slender, usually curled, truncate, about equal in length to half the 

 breadth of the body ; it is a tubular organ, with a slit along the 

 lower side, formed by the rolling up of a long, thin, membranous 

 process. At the posterior edge of the tubercle there is a shorter, 

 flat pointed process, connected with the female organs. Color of 

 dorsal surface yellowish-brown, lighter or darker and reticulated with 

 dark brown, often specked with flake-white ; gill and proboscis dark 

 purplish-brown ; the proboscis with a darker dorsal patch ; tentacles 

 sometimes crossed by dark brown bands. Foot salmon -color. 

 Odontophore very large and broad, with 150 to 170 rows of teeth ; 

 no median teeth ; all the teeth are similar in structure, and show 

 only a gradual change in form and size from the inner to the outer 

 ones. The inner ones are elongated, slightly curved, narrow-lanceo- 

 late, with a very acute point and with a smaller, narrow, sharp den- 

 ticle on the inner edge, parallel to but shorter than the main poiiit ; 

 the outer teeth gradually become shorter, blunter, with a smaller 

 denticle, which finally nearly disappears. Length, usually 30 to 

 40 ; breadth, 10 to 14 mill. ( F.). 



In the best preserved specimens the reproductive organs are often 

 protruded, the forms of the different organs varying with the state 

 of extension. The verge or most anterior organ, when fully 

 extended, is long, cylindrical or a little clavate, with rows of minute 

 recurved hooks near the end, and terminated by a slender curved 

 spicule. The most posterior opening (urinal) is just at the anterior 

 base of the gill, in the form of a small papilla, with a central open- 

 ing. Between these there are two organs, on a more or less swollen 

 common base ; the more anterior is a large opening with raised mar- 

 gin ; a little behind and below this is a long, exsert, flat, usually 

 tapered and acute, copulatory organ, varying much in size and form 

 according to the state of extension. All these organs can be so re- 

 tracted as not to be noticeable, but this seldom happens in alcoholic 

 specimens, most of which show the organs more or less extended. 

 The anal orifice is behind the base of the gill. ( Verrill.'). 



20 miles south of Block Island, in 38 fathoms ; about 70 to 100 

 miles south and southwest from Martha's Vineyard, in 28 to 310 

 fathoms, both on bottoms of mud and of fine, compact sand, very 

 abundant ; Off Chesapeake Bay, in 31 to 300 fathoms ; Off Delaware 

 Bay, in 130 and 156 fathoms. 



With this species, and probably belonging to it, we often took 

 gelatinous, but rather firm, cylindrical egg-clusters, about 20 mill. 



