9 



the other this is never observed. The young thus adhering 

 are never of the full size of the parent: a circumstance not 

 easily accounted for; as it seems impossible that they should 

 at any time after their first stages of growth, be able to 

 loosen their hold and assume a new station. 



The researches of Mr. Thompson have made the history 

 of this class of animals important, by showing their close 

 affinitv with Crabs and Lobsters. 



* A. ANSERIFERA. Lepas A. Turt. Lin. Mont. Test. 



Brit., vol. 1, p. 16. Stew. Elem., vol. 2, p. 364. Common 

 Barnacle. Common on floating wood that has been long 

 at sea. Its distinctions from the A. Levis have been 

 already pointed out. The stalk, which is from a foot to 

 18 inches in length, is capable of voluntary motion, in- 

 cluding contraction and extension; and a point of support 

 for lateral bending is afforded by compressing a portion 

 of fluid into the requisite limited space. 



* A. FASCICULARIS. Lepas F. Mont. Test. Brit., vol. 



2, p. 557. In no volume to which I have access do I find 

 a satisfactory description of this species ; it may therefore 

 properly find a place here. Length of the shell, 7 tenths 

 of an inch, depth 5| tenths ; the thickness or inflation con- 

 siderable, the cross segment forming an oval posteriorly ; 

 texture of the plates thin as tissue paper, and easily broken. 

 The dorsal plate is remarkably arched, wide, and ter- 

 minating circularly above the stalk. The orifice gaping. 

 Anterior lateral plate small, slender, jagged at its point; 

 the larger plate with an everted hinder margin. Colour 

 whitish, with tints of blue, the soft parts appearing through 

 the texture. The stalk short, small, fixed in a tumid bed 

 of soft membranous substance ; and the animals project at 

 right angles to the substance on which they are fixed ; 

 adhering in clusters, but each standing out in as opposite 

 a direction as possible from those with which it is asso- 

 ciated. 



This is a rare species, since it was but barely known to 

 the industrious researches of Montagu. I have met with it 

 attached to the stalk of sea weeds ; and once in considerable 

 quantity, thrown on shore in a storm. It is a stranger cir- 

 cumstance that I possess some specimens, intermingled with 

 the equally rare species, A. Sulcata, and both attached to a 

 feather of the wing of a gull. 



A. SULCATA. Lepas S. Mont. Test. Brit., vol. 1, p. 17, 

 pi. 1, fig. 6. Length of the shell 7 tenths of an inch, 

 depth 4^ tenths. The larger plates are moderately in- 

 flated behind, overlapping at the hinge below; the anterior 

 plates small ; dorsal plate not running to the point. The 

 side plates are thickly covered with raised lines proceeding 



c 



