488 PROCEEDIXGS OF THE GEOLOGICAL SOCIETY. [Juiie 7, 



" The form of the dorsal plates^of this species is subtriangular, the 

 posterior edges making very nearly a right angle. The lateral angles 

 are rounded, and the anterior edge is very sinuous. All the plates 

 are supplied with a well-marked median carina, and appear to have 

 been without apophyses. The surface is covered with a small num- 

 ber of equidistant striae. The test is slender. The median area is 

 larger than the lateral ones. 



" This Chiton," M. deKoninck adds, "resembles Chiton Loftusia- 

 oius, King, but differs from it in the regularity of the striae of the 

 median and lateral areas, and by the more marked sinuosity of the 

 anterior edge of its plates." 



From an examination of the" figures of the very beautiful speci- 

 mens (Plate XIY. figs. 1 a-7i) it will be seen that we have evidence of 

 two principal rows of inequilateral plates (Plate XIV. figs. 1 1, A:,), each 

 with a strong median carina, and having their edges intersecting 

 each other. Upon the two external margins can also be traced the 

 remains of two other rows of much smaller plates, without a keel, 

 but similarly ornamented with delicate hues of elevated striae, which 

 follow, as in the larger valves, the contour of the plate (see Plate XIV. 

 fig. ] I). Two specimens show as many as eleven plates in one 

 series, and one about fifteen. 



Having pointed out the objections to Chiton Wrightianus being 

 accepted as a Chiton, it devolves upon me to show my reasons 

 for considering it a Cirripede. 



The first point of affinity is the ornamentation of the valves. 

 This becomes at once apparent by comparing them with the oper- 

 cular valves of Balanus (especially the tergum (Plate XIV. fig. 5), 

 or of Pollicipes (Plate XIV. fig. 3). 



Secondly, the plates have their overlapping points directed 

 upwards, or towards what I believe to have been the aperture 

 of the shell. This agrees with the structure of the Cirri])edes, 

 for Mr. Darwin has demonstrated that they are attached by their 

 anterior extremity, the peduncle in the Lepadidce being the cephalo- 

 thorax greatly produced, 



Thirdly, the rows of imbricated plates, with their intersecting 

 edges, cannot be compared with any other order except Cirripedia, 

 unless it be the Echinodermata, from which they differ in the 

 absence of any trace of crystalline structure, and in the sculpturing 

 of the valves ; whereas the peduncles of ScaJpellum ornatum 

 (Plate XIV. fig. 4), Loricida pulchella (Plate XIV. fig. 2), PoUicipes 

 Redtenhacheri, and P. cornucopia all indicate an analogous arrange- 

 ment of the plates. Indeed, the shell of every Balamis is composed 

 of a series of intersecting plates arranged around the soft body of 

 the animal. 



From the imperfect condition of the specimens, it is probable 

 that the animal was attached by its side as well as its very slender 

 base, as appears to have been the case in Loricida and in several 

 Upper Silurian Cystideans. The opercular valves we do not know 

 at present ; but they were no doubt small, as the size of the scales 

 would indicate that (as in Loricida and the recent genera, Lithotrya 



