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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1854 Excerpt: ...the two lower lines of the table. I believe that variability l this degree is very uncommon in other cirripedes, though, as stated in the Introduction, the number of the segments always increases With the growth of the individual. The terminal segments in the longer rami of both the first and third cirrus are antenniformed, ----being elongated, and of a different shape, with fewer bristles, compared with the basal segments of the same cirri. It is apparently these terminal segments which are particularly liable to vary in number. In both rami of the third cirrus, some of the segments, from the sixth to the eleventh inclusive, (counting from the bottom), more especially the eighth, ninth, and tenth, carry a few spines coarsely and doubly pectinated; but as some of the adjoining segments carry spines which may be called doubly serrated, it is not easy to draw an exact line of demarcation. Sometimes, though rarely, a few of the nearly terminal segments in the second cirrus are furnished with similar, doubly pectinated spines. Numbers qf the segments in t/ze rmni of the Cirri, in diferent Varieties.--Under the generic description, I have stated that after having spent some time in examining a very large suite of specimens ot T. porose, I concluded that at least four of the varieties were true species It so happened that all the specimens which I first examined of the var (4) mbescena, had the narrow sloping terga, and senta with only two or three great teeth on their occludent margins; but ultimately, in a group thus characterised, I found one or two individuals with terga pg'-egisplly of tlie shape of those' in var. (1) cornmunig. 11gaiin, lin a group 0 u nr e s ecimens 0 var. communw, a ew a t e narrow sloping tzrgiil, and, senta with teeth on their...

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