FOSSIL CIRRIPEDES FROM NEW ZEALAND. 847 



absence of a sutural edge to abut against the longitviclinal liclge 

 on the inner surface. All these are primitive characters, and 

 show that in this Cirripede we have a Balanid more primitive 

 than Balanus. 



In my preliminary consideration of this form I regarded it as 

 being related, mainly in the absence of radii, to the recent species 

 Bcdanus Mrsutus and B. corolliformis, which were included by 

 Dr. Hoek * in a new section (G) of Bcdanus, and B. hoekianus 

 and B. callistoderma, which were referred by Dr. Pilsbry f to the 

 same section, and I intended to found a new genus to include 

 these species. On seeing a proof of Dr. Hoek's work (1913, 

 ' Siboga-Expeditie, Oirripedia-Sessilia,' pp. 244-246), however, 

 I found that he had included these I'ecent species, together with 

 two new species {H. velutinum and H. arafurae), in a new genus 

 Hexelasnia. 



Dr. Hoek kindly sent me drawings of the type-species H. velu- 

 timcm, and from these it could be seen that while Hexelasma 

 differs from Balanus in the absence of I'adii and the absence of 

 longitudinal ribs on the inner svirface, it agrees in having a, well- 

 developed sheath, and in the carino-lateral compartments having 

 an upturned extension of the alas as well as a well-developed 

 sutural edge. 



Since " PolUcipes (?) aucklandicus " agrees with Hexelasma in 

 the absence of radii and of longitudinal ribs on the inner surface, 

 it seems advisable to refer it to that genus ; but in some respects 

 it appears to be somewhat more primitive than the typical species 

 of Hexelasma, especially in the feeble development of the sheath, 

 in the absence of a distinct upward extension to the alse of the 

 carino-lateral compartments, and of a sutural edge to the alse of 

 the carino-lateral compartments. 



The species included in Hexelasma are all deep-sea forms, and 

 occur at depths varying from about 100 to 900 m. In length 

 the shell of the largest species, H. corolliforme Hoek, measures 

 nearly 45 mm., and since the largest-known compartment of the 

 fossil H. aiicMandicum measvires about 190 mm., the great 

 ■difference in size is apparent. 



Except for Balanus psittacus Molina sp., which has been known 

 to attain a length of 9 inches (circa 225 mm.), Hexelasma auck- 

 landicum is the largest-known Cirripede. Balanus ever^nanni 

 Pilsbry, another large barnacle, is recorded as measuring 150 mm. 



Hexelasma sp. 



A large number of the disconnected compartments of a small 

 Balanid are to be seen scattered about in the matrix containino- 



* 1883. P. P. C. Hoek, ' Clialleuger ' Report, Zoology, vol. viii. pp. 155-160. 

 t 1911. H. Pilsbry, " Barnacles of Japan and Bering Sea," Bull. Bureau 

 Fisheries, Washington, vol. xxix. 1909, pp. 76-80. 



