Contributions to the knowledge of the alpheid shrimp of the Pacific Ocean. Part XVIII: a new species of the genus Alpheus from the mouth of the Sepik River, New Guinea
Abstract
[Excerpt from Discussion p. 263]. The compressed large chela, the shape of the orbitorostral front and the flattened dactyli of the third legs, among other characteristics plainly put this species in the Brevirostris group of the genus Alpheus. As far as we have been able to determine the distal broadening and proximal tapering of the palm of the large chela and its extreme compression are unique to the group. Further characteristics separate this species from previously known species. It can easily be separated from many in the group by the lack of transverse notch behind the dactylar articulation of the large chela, and by the fact that the rostral crest or ridge does not extend posteriorly to well behind the orbital hoods. The description and figures of A. halesi Kirk (1887: 194, pl. 6d) leaves ambiguities, but the heavy longitudinal ridge on the outer face of the large chela plainly separates it from this species. A. macroskeles Alcock & Anderson ("correct original spelling" as defined in International Rules of Zoological Nomenclature, Article 32 (a) (ii)) (1894: 153), A. distinguendus De Man (1909: 155, pl. 7, fig. 9–14), A. pustulosus Banner & Banner (1968: 143, fig. 2), A. nonalter Kensley (1968: 172, fig. 15) and A. stephensoni Banner and Smalley (1969: 45, fig. 2) have some manner of armature, either spines or teeth on merus of the large and small chelae, and only in A. distinguendus is the palm of the small chela of the male shorter than the fingers. In A. stephensoni the palm of the small chela of the male is about equal in length to the fingers, not markedly shorter than the fingers as in this species.
