1851.] 243 



Found often in great numbers, adhering with considerable tenacity by means of 

 the posterior constricted extremity of the bodj', to the under surface of the bran- 

 chial covers, the branchial laminas, and to the extremities, especially in the vicini- 

 ty of the joints. 



Remarks. When the king crab is removed from the water, its planaroid para- 

 site retires to the deepest recesses between the limbs and other external organs 

 to avoid evaporation. The parasite moves with a gliding motion like the species 

 of Planaria, and also by fixing the posterior extremity and extending the anterior 

 part of the body to its greatest length, and then abruptly detaching and drawing 

 forward the former, like the leeches. At other times it fixes itself posteriorly, 

 and waves the anterior portion of the body to and fro through the water. 



Attached to the branchial lamina; of the king-crab, are frequently observed 

 ochreous or brownish, oval, compressed cysts, from ith to 2 lines long, and l-6th 

 to 1 line broad, attached by a short pedicle at one extremity, and unusually close- 

 ly applied to the surfaces between the branchial laminae, which are receptacles 

 or ova ? of the Bdelloura parasitica. Occasionally the margin of the cysts 

 is provided with a fringe of short, irregular, blackish filaments. Sometimes these 

 cysts exist in such numbers as to have the appearance of flaxseed sprinkled be- 

 tween the branchial laminae. 



6. Bdelloura rustica, n. s. 



Body brownish or blackish, translucent, lanceolate; anteriorly narrowed, ob- 

 tuse ; lateral margins thin, undulating ; constricted portion truncated posteriorly, 

 with parallel margins. Eyes two, reniform. ffisophagus simple, cylindrical. 



Length 2 to 3 lines; breadth 2-5ths to 4-5thsof a line. 



Habitation. Egg Harbor bay. New Jersey, upon Ulva latissama, Li?in. 



RemarZs. Movements same as in the preceding species. When free in water 

 it moves with great rapidity, and rises to the surface in the manner of the leech, 

 or the larva of the gnat. 



Gen. nov. MYZOBDELLA.* 

 Body elongated, compressed fusiform, smooth. Head continuous with the body, 

 subindibuliform, obliquely ventrally terminal. Mouth central, unarmed. Ace- 

 tabulum ventrally obliquely terminal, concave, not corneous. 



7. Myzobdella lugubris, n. s. 



Body cylindro-fusiform, in transverse section, elliptical, black olivaceous 

 green ; anteriorly narrowed, cylindroid ; posteriorly incrassate. From 15 to 18 

 annulations. Integument translucent, permitting the sacculated intestine of a 

 black green hue, to be visible. Acetabulum circular, concave, a little larger than 

 the oral disk. 



When elongated 10 lines, by i line in breadth posteriorly, l-5th of a line ante- 

 riorly. Will contract to 4 lines by 4-5ths line in breadth. 



HabitatioJi. Parasitic upon the common edible crab, Lupa dicantha, M. Edw.' 

 usually found attached about the base of the limbs. 



MECKELIA, Leucicart. 



8. Meckelta lactea, n. s. 



Body very soft, milk white, in transverse section lenticular, convex above and 

 below ; when extended, very much compressed, more especially posteriorly, in- 



*^D^w, I suck ; jiSSfTiXa, a leech. 

 32* 



