CATOPHRAGMUS POLYMERIAS. 489 



shell, excepting in old worn-down specimens, increases largely by dia- 

 metric growth : during the diametric growth, the outer scales must be 

 laterally separated a little from each other, and probably they are late- 

 rally added to ; but there are no distinct lines of suture, or rows of 

 smaller scales, corresponding with the sutures between the eight inner 

 compartments. The alse do not project much ; their edges, as well as 

 the shoulders into which they fit, are generally irregularly crenated : 

 they are added to during diametric growth above the line of attachment 

 of the opercular membrane. There is no appearance of radii ; but as the 

 eight inner compartments are added to laterally, and are often cre- 

 nated, on the edges which correspond with the radii in other Cirripedes, 

 such edges must be considered as radii. 



With respect to the scales in the several outer whorls, they resemble 

 each other except in size, and the outermost scales are reduced to mere 

 transversely elongated beads. Their basal edges are concave inwards, 

 being bent like the ridge of a house ; hence sub -triangular spaces or 

 tubes, lined by the corium, run up between the scales. When per- 

 fectly preserved, the outline of each scale is a much elongated triangle, 

 but usually, from their summits having been worn off, the outline is 

 nearly that of a parallelogram. Their basal edges are dentated, and 

 their upper parts, both on the outside and inside, are marked, where 

 joined to the other compartments, by slight calcareous ridges : outside, 

 there are longitudinal shoulders (PL 20, fig. 4 b), caused by the 

 lateral overlapping of the adjoining scales ; these are best seen in sec- 

 tion in corroded specimens (fig. 4 d) : on the inside there are, also, 

 in the upper part, slight medial longitudinal ridges, caused by the 

 sutures, which the scales have covered. 



In large old specimens there are ten, or even more, whorls of com- 

 partments, but it is scarcely possible to count them with any accuracy. 

 The first whorl consists of the eight large inner compartments, though, 

 homologically, it is doubtful whether the rostro-lateral compartments 

 in any sessile cirripede really belong to the same whorl with the others. 

 The second whorl consists of eight smaller pieces, covering the eight 

 sutures in the first whorl (see the tracing of the basal edges of all the 

 compartments and valves in a very perfect specimen, PL 20, fig. 4 c). 

 The third whorl, in large and perfect specimens, consists of twice the 

 number, or sixteen, still smaller scales, corresponding with the sixteen 

 sutures of the second whorl ; but sometimes there are less than sixteen 

 pieces, owing to some of the scales being large enough to cover two 

 adjoining sutures as well as the intermediate portion of the compart- 

 ments of the first whorl. In the fourth whorl, instead of there being, 

 even in the most perfect specimens, twice sixteen, or thirty-two pieces, 

 there are only twenty-four ; this being caused by single pieces (placed 

 alternately with two pieces) being broad enough to cover two sutures 

 as well as the intermediate portion of the compartment of the third 

 whorl. In the succeeding whorls this same arrangement seems to be 

 the usual one, so that in the fifth whorl, instead of there being, in the 

 most perfect specimens, twice twenty-four, or forty-eight pieces, that 

 is, twice the number in the last whorl, there are only thirty-six scales, 

 or once and a half as many scales. 



