[Read before Wellington Branch, November 29, 1950; received by Editor, February 19, 1951]

This study is part of a series assisted by a grant-in-aid of research from the University Research Grants Committee.

This paper identifies and describes the early-settled, post-larval stages of the crab, Eurynolambrus australis M-E. and L., which is a common endemic species found at the lower tidal levels on stony and rocky coasts. These post-larval stages are of the greatest value in the determination of the systematic status of this species, which was originally (1841) placed in the Parthenopidae and accepted as a member of this family by Dana, Miers (1876), and by Filhol (1885). In 1879, Miers transferred the species to the “Cancerinae”, as being intermediate between the latter and the Parthenopidae, since while there is marked resemblance to Cryptopodia as in the expanded triangular form of the carapace, etc., Miers considered that the orbital and antennal regions show affinity with Cancer—the front being bilobate, the flagellum excluded from the orbital hiatus, the anterior legs not trigoniform, and essentially the legs not concealed by the carapace.

Flipse (1930) reviews the Parthenopidae, and apparently accepts Miers’ conclusion, for he quotes Miers (1879) and makes no further reference to Eurynolambrus in this review. The adult E. australis has a superficial cancroid facies. The oxyrhynchous characteristics are minimised by this adoption of this cancroid form, and meticulous examination of even the adult brings the status of the species as a parthenopid into doubt. The chelipeds, though long only in the largest specimens, are reasonably mobile and the fingers not markedly bent on the hand. Hooked hairs are present. As Miers determined, the second joint of the antenna is actually large, firmly attached to the epistome, and providing an incomplete floor to the orbit so that the orbits are relatively well-formed; but all of these characters refer more to the Majidae than the Parthenopidae and still less so to the Cancridae. In the Cancridae, as known to me in Cancer novae-zealandiae, the orbit is floored largely by an infraorbital plate from below and the second segment of the antenna forms only a small portion of the floor.

The post-larval stages described below remove all doubt from the status of E. australis as an oxyrhynch. The well-developed, divergent rostra; the incomplete orbit consisting of a supraocular eave, a cupped postocular process, and an intervening spine; the open ventral aspect of the orbit; dorsal turbercles; hooked hairs, used for masking; the enlarged second segment of the antenna carrying an anterior and an anterolateral spine; all these features and the general facies are

oxyrhynchous (Rathbun, 1925). There is no resemblance to the brachyrhynch post-larval stages as known to me.

The position of E. australis in the Oxyrhyncha is difficult to establish, since I have been unable to obtain data on the early settled stages of these crabs. The Parthenopidae are not otherwise known for New Zealand, but the Majidae are represented here by several species. The many features of both adult and post-larval stages compared, with our maioids indicate that E. australis is more correctly a member of the Majidae, and should probably be placed in the Pisinae, where it represents an advanced condition in completion of that type of orbit since there is the large, blunt, cupped post-ocular process into which the eye can be retracted, but with the cornea still visible from above and definitely more so from below; a supraocular eave; short eye-stalks; proximally wide, distally toothed second segment of the antenna; bilobed rostrum; subequal width to the merus and ischium of the external maxillipeds; and a long slender first male pleopod, while the second is short (Stephenson, 1945).

The first received, the larger of these post-larval specimens, was sent by Mr. J. T. Morton, who collected it from the holdfast of Macrocystis washed up at Island Bay, December, 1948. This was originally recognised as a maioid, but was unassignable to any of our species until the conformation of the posterolateral margin was recognised as suggesting E. australis, and subsequently the sub-hepatic cavern was seen as common to the young and the adult of the species. The smaller specimens were then found in a collection from Chatham Island (September, 1948) in company with Galathea pusillus and a post-larval specimen of Pilumnus sp. Fortunately, the smaller and larger specimens appear separated by at least one moult, giving an indication of the slow assumption of the specific form. The detailed morphology is drawn from the larger specimen, which differs in no significant respects, other than proportionally, from the smaller. Both specimens were liberally masked with sand-grains when first received.