REPORT ON THE CIRRIPEDIA. 51 



Megalcosma striatum, n. sp. (PI. II. figs. 5-9 ; PI. VII. figs. 8-9). 



With the characters of the o-enus. 



General appearance. — The capitulum is large and resembles much in outline the 

 shell of a Lamellibranchiate Mollusk. The short peduncle is quite covered by the 

 capitulum. The shape of the capitulum is very characteristic ; it is ovate, with both 

 extremities pointed, the occludent margin being almost exactly of the same length as 

 the carinal margin. All the valves are beautifully and distinctly striated and covered 

 by membrane, which is not very persistent, except over the lines separating the 

 valves. 



Scutum triangular, or more exactly still, having the form of a sector of a circle, a little 

 more than 90°. The two radii are represented by the tergo-lateral and carinal margins 

 of the valves. The basal margin seems to be totally wanting ; most probably, however, 

 it is represented by the undermost part of the occludent margin. The scutum is divided 

 into two unequal parts by a very prominent ridge which runs from the angle (formed by 

 the tergodateral and carinal margins) to the occludent margin, which it meets at one-fifth 

 of the whole length of the occludent margin. The two unequal parts of the scutum 

 separated by this ridge have their lines of growth in a very different direction ; those of 

 the larger part run exactly parallel to the tergo-lateral margin, those of the smaller 

 undermost part converge to meet at the angle formed by the carinal and occludent 

 margins. From the point where the ridge meets the occludent margin to its apex, the 

 scutum shows externally a prominent and flattened border, much broader at the apex 

 than at the other extremity, and as far as this border goes, a margin distinctly bent down, 

 which together probably represent the small part, that, in the nearly related genera of 

 Lepadids, is situated between the occludent margin and the ridge which runs from the 

 apex to the umbo. Internally (PI. VII. fig. 8), this margin projects as a very prominent 

 ridge downwards, terminating in both scuta in a very large tooth. This is situated at a 

 distance of about one-fifth of the length of the occludent margin from the angle formed by 

 the occludent and carinal margins, and has a flat surface of a long oval form ; on both two 

 small notches are easily observed. As shown by a dorsal (carinal) view of the animal 

 (PL II. fig. 6), the undermost part of the scutum is considerably expanded on both sides. 

 Parallel to the lines of growth the scuta are distinctly striated, the surface of the different 

 stripes being again transversely, but very minutely striated. In my figure (PI. II. fig. 5) 

 these latter strife have not been represented. Internally, near the carinal margin, a very 

 small notch is visible for the reception of a tooth of the carina ; the tergo-lateral 

 margin shows an indistinct tooth near both extremities ; these, of course, serve also 

 for the attachment of the other valves. The smaller undermost part of the scutum has 

 on its surface still another ridge, which describes with its continuation situated on the 

 carina half a circle, as will be easily understood from fig. 5 on PI. II. 



