42 Clark — Two New Australian Crinoids. 



diHtally ; I\ (> mm. long, stouter and stiffer than Pj, being, in fact, the 

 largest and longest pinnule on the arm, with about eighteen joints, the 

 first two approximately twice as l)roa(l as long, the third squarish, the 

 remainder a])out half again as long as broad; the pinnule is smootli, the 

 joints being without lateral processes or everted ends; Pg 3 mm. long, 

 small and weak, nearly as large basally as Pj, but tapering more rapidly, 

 with tliirteen joints, the first short, the following increasing in length to 

 the fourth, which is squarish, and further increasing to a length of about 

 twice the breadth in the terminal portion ; following pinnules similar, 

 sf)on l)ec(>ming more slender and gradually increasing in length; distal 

 pinnules very slender and hair-like, al)out 7 mm. long, with twenty-three 

 joints, the tir.<t short and crescentic, the second nearly as long as l>road, 

 slightly less in diameter anteriorly than posteriorly, the third squarish, 

 the remainder about half again as long as broad, becoming about twice 

 as long as broad in the distal portion. 



Color (in sjjirits). — Brownish-purple, the cirri and dorsal surface 

 lighter. 



Ti/pc locality. — Dirk Hartog Island, west Australia; 7 fathoms. 



JiCmarks. — This new form is readily distingxnsliable from the ten previ- 

 ously described species of the genus; the elongate Pj of 0. hich'Ds, as well 

 as the two dorsal processes on its cirrus joints, the very numerous cirrus 

 joints of 0. graciltcirra, the short stout cirrus joints of 0. pinniformis, 

 the single dorsal spine on the few stout cirrus joints of 0. caribbea, the 

 strong imbrication of the brachials of 0. imbricata, and the spines or 

 lateral processes on the proximal pinnules of 0. yracilicirra, 0. carpen- 

 teri, O. japonica, 0. piilchella and 0. strripinna separate them at once. 

 The elongate proximal pinnules described in 0. adconx would serve to 

 ditlerentiate it, if adco)ue should be shown to really belong to the genus 

 Oligovii'tra. 



Oligomc'tra studeri is most closely related to the group of species typified 

 by 0. serripinna. 



