574 ORDER ABDOMIXALIA. 



carapace : its ventral surface is flattened, and is formed of 

 somewhat thickened membrane : on each side, a little below 

 the articulation separating this segment from the mouth, 

 there is a small blunt projection, with the free part only 

 ^th of an inch in length. Each of these appendages bears 

 four or five bristles on one side near the summit, and a few 

 on the other side, lower down : from their position I be- 

 lieve them to be rudiments of a first pair of maxillipeds 

 (tetartognathites of Milne Edwards), of which no trace occurs 

 in any other cirripede. The differences between this seg- 

 ment and the seven succeeding segments, is of interest, as 

 offering some confirmation of the belief, lately disputed by 

 some naturalists, that the cephalic and thoracic segments in 

 the class Crustacea, do differ in their nature, — a conclusion 

 which we shall see further confirmed under Proteolepas. 

 The second and third {i. e. first and second thoracic) seg- 

 ments (2, 3, fig. 5) are the next largest, and are remarkable 

 from supporting singular appendages, already alluded to. 

 The sides of the second segment are formed of thickened 

 yellowish membrane. The fifth and sixth segments are the 

 smallest, and mark the point of chief flexure of the body. 

 The eighth segment is a little elongated, formed of thicker 

 membrane than the other segments, and dorsally is indented 

 by the anus. 



The singular tapering appendages (fig. 5, i, k) arising dor- 

 sally from the second and third segments, differ from each 

 other only by the upper one being smaller, less curled, and 

 perhaps rather smoother. When first examining this animal, 

 not knowing that it was female, and not finding a probos- 

 ciformed penis, I concluded that these organs were of 

 this nature, — an excusable mistake, considering their 

 almost ringed structure, their somewhat constricted bases, 

 the direction of their curvature, and their position in the 

 midst of the ova within the sack. On careful examination, 

 however, these appendages are seen not to be truly ringed 

 or articulated, but are covered with transverse lines of 

 scales, hirsute on their edges ; these scales being less dis- 

 tinct, or even quite absent on the smooth upper portion ; 

 they do not include any muscles ; they are imperforate 

 at the apex, which is not furnished with bristles (as seems 



