26 F. Chci'pinan : 



Family — Pah^ophiuridae. 

 Genus — Sturtziira, Gregory, 1897. 



Stuptzura leptosomoides, sp. nov. 

 (PL VII., PI. VIIL, Fig. 4). 



Description. — Arms very flexible, moderately broad in the 

 middle, very slender towards the distal end. Disc not visible in 

 specimens now described. Mouth -frames slender, separate, 

 shorter than the jaws. Oral framework having a diameter of 

 4 mm. in our examples. Ambulacral ossicles subquadrate, 

 broader proximally, with a podial sinus on the distal and outer 

 faces. Adambulacrals narrow, curved, fusiform, and disposed 

 obliquely, extending outwards towards the arm-tips. Intermediate 

 spine-bearing plates with two or three prominent spines. 



Measurement of type specimen. — 



Length of arm - - - - - - 10 mm. 



Width of arm at broadest part, viz., 3 mm. ") ^ ^^p. 



from junction with mouth-frame ')"""" 



Diameter of oral pentagon - - - 2.5 mm. 



Observations. — P. brisingoides was selected by Gregory as the 

 type of the above genus,' but since that species appears to require 

 a somewhat different explanation as to its arm structure, which 

 is related to that of the protasterids, as already shown here, 

 Sturtzura leptosoma, Salter sp.,^ must now be regarded as the 

 type form. The present species resembles, at first sight, S. lep- 

 tosoma of the Ludlow beds of the Welsh border so closely that 

 the English and Victorian fossils appeared to be one and the same 

 species. Upon examining their arm-structure, however, it is seen 

 that although generically related, the forms are specifically dis- 

 tinct (see pi. viii., figs. 4, 5). 



Horizon and Locality. — Silurian (Melbournian), Moonee Ponds 

 Creek, Flemington. Geol. Surv. Coll. 



1 Proc. Zool Soc. (1896), 1897, p. 1034. 



2 Ann. Mag. Nat. Hist., ser ii., vol. xx., 1857, p. 331, pi. ix., fig. 5. 



