SCALPELLUM 333 



It is of importance also to know the changes undergone during the ontogeny of a species, 

 as here shown for S. gibber urn. 



My study of the young stages of certain species of Scalpellum brings out the fact that 

 young specimens of many closely allied forms of Scalpellum are difficult to distinguish. 

 Thus, I find that young stages of S. gibberum closely resemble those of S. scalpellum 

 figured by Broch (1924). But, in the older stages, the diff'erences become greater and 

 greater, for the umbo of some plates, such as the scutum, has a different position. The 

 primary part of the inframedian latus is very different in both these certainly allied 

 species. The inframedian latus in the allied species -S. stearnsi, Pilsbry, 1890, is of the 

 same type as in S. gibberwn, the primary part being triangular with a basal umbo. 

 Pilsbry (191 1) figures a stage of S. stearnsi much like the eighth stage here figured 

 (Fig. 2, b). But S. stearnsi is in other plates, for instance the scutum, more like S. scal- 

 pellum. The differences in these three species seem to have arisen through the secondary 

 development of the accessory parts of the plates, except in the inframedian latus. The 

 scales of the peduncle are, in S. scalpellum and S. stearnsi, more different from the fully 

 grown stage of S. gibberum, but by studying the young stages of this latter species, we 

 have here seen that the scales were also originally transversely elongated. 



Scalpellum liberum, n.sp. 



St. 187. 18. iii. 27. Neumayer Channel, Palmer Archipelago. 64° 48' 30" S, 63° 31' 30" W. 

 259 m., m. Gear DLH. Three full-grown specimens situated on a Gorgonian. 



HoLOTYPE. Zoological Department of the British Museum. 



Diagnosis. Female. Capitulum with fourteen well-calcified plates, beautifully 

 sculptured with growth lines and longitudinal lines. Scutum quadrangular, with 

 straight occludent margin, and projecting apex. Tergum large, triangular, with bowed 

 margins. Carina regularly bent; dorsal roof convex in the middle, with indistinctly 

 indicated lateral ridges. Upper latus triangular, with apical, projecting umbo. Rostrum 

 triangular, umbo apical. Rostral latus triangular. Inframedian latus triangular, with 

 apical umbo, the upper part of the plate projecting freely. Carinal latus triangular, with 

 much projecting apical umbo. Peduncle well developed, with very large triangular 

 scales regularly covering the whole surface. Mandible with three teeth and an inner 

 angle divided into two pectinated teeth. Maxilla I with a very small notch. Maxilla II 

 with bristles in two groups. Caudal appendage single-jointed, without bristles, of the 

 same length as the proximal segment of the protopodite. 



Complemental male sack-like, without valves but with a distal projection with rudi- 

 ments of cirri. 



Description. This beautiful species is well distinguished from the known 

 species. It is more nearly related to S. velutinum, Hoek, 1883, in the shape of the 

 carinal latus, and consequently belongs to the group of S. velutinum, Pilsbry, 1907. 

 I have named this new species S. liberum from the very typical freely projecting 

 inframedian latus. 



