MOUTH. 39 



The shape of the body varies, owing to the greater or less 

 development of the lower part of the prosoma, the greater 

 or less distance of the first from the second pair of cirri, 

 and of the mouth from the adductor scutorum muscle, 

 (PL IX, fig. 4, and PI. IV, 8a). In all the genera, the body 

 is much flattened. I may here mention a few particulars 

 about the muscular system. One of the largest muscular 

 masses is formed by the adductor scutorum, and by the 

 muscles which surround in a double layer (the fasciae 

 being oblique to each other) the whole of the upper part 

 of the prosoma. From under the adductor, a pair of 

 delicate muscles runs to the basal edge of the labrum, so 

 as to retract the whole mouth, and two other pair to the 

 integument between the mouth and the adductor, so as 

 to fold it -. again, there are other delicate muscles in some 

 (for instance in Zepas Hillii) if not in all the Lepadidae, 

 crossing each other in the most singular loops, and serving 

 apparently to fold the membrane between the occludent 

 edges of the scuta. Within the prosoma there is a strong 

 adductor muscle, running straight from side to side, for 

 the purpose, as it appears, of flattening the body. The 

 thorax, on the dorsal and ventral surfaces, is well fur- 

 nished with straight and oblique muscles (without striae), 

 which straighten and curl up this part of the body. The 

 muscles running into the pedicels of the cirri, cross each 

 other on the ventral surface of the thorax ; the muscles 

 within the rami are attached to the upper segments of 

 the pedicels. Finally, I may remark that the whole of the 

 body and the cirri are capable of many diversified move- 

 ments. 



Month. — This is prominent, and almost probosci- 

 formed (PL IX, fig. 4 b), and in the abnormal Anelasma 

 (PL IV, fig. 2 d), quite probosciformed, — such, also, was 

 its character in the larval condition. In outline, it is either 

 sub -triangular, or oval with the longer axis transverse ; the 

 whole is capable, as well as the separate organs, of con- 

 siderable movement, as I have seen in living sessile 

 Cirripedes. It is composed (Tab. V, fig. 2) of a labrum, 



