ON A SYNTHETIC TYPE OE OPHIUEID. 73 



Balanfs CEENATFS. 



Balanus crenatus, Bruguiere, Darwin, Monogr. Cirripedia, Balanidce, 

 p. 261, pi. vi. fig. 6 (1854). 



I refer here, but with some hesitation, a small specimen col- 

 lected in Discovery Bay at 30 fathoms. The shell is regularly 

 and steeply conical, white, the compartments smooth, without lon- 

 gitudinal carina?, except one, rather obscure, on the carinal valve ; 

 the radii are very oblique, the opercular valves much thinner than 

 is usual in B. crenatus ; the scutum has, however, scarcely any 

 trace of an adductor ridge, and the spur of the tergum is rounded, 

 but rather longer than in Darwin's figure of that of B. crenatus, 

 and placed at rather less than its own width from the horizontal 

 angle. The walls of the shell are internally ribbed. Specimens 

 of B. porcatus were collected at the same locality in 20 fathoms. 



On a Synthetic Type of Ophiurid from the North Atlantic. 

 By Prof. P. Martin Duncan, F.E.S., E.L.S., &c. 



[Read December 4. 1879.] 



(Plate III.) 



Theee is a very remarkable Ophiuran which forms part of a col- 

 lection obtained by Dr. Wallich, during his voyage in H.M.S. 

 'Bulldog' in the year 1860, off the coast of East Greenland. 

 The Ophiuran was presented by him to the Eoyal Microscopical 

 Society, and I have been permitted to examine and describe it. 



At first sight, the little form might be considered to be an Am- 

 phiuran of the Hemipholis group, but a glimpse at the upper part 

 of the disk and at the sides of the arms discovers a spinulose con- 

 dition of the upper surface of the first and a hooked arrangement of 

 thelatter structures. The resemblance to species of Ophiothrix then 

 becomes more or less striking ; but the large scaling of the disk, 

 the absence of the tooth-papillae, and the presence of accessory 

 pieces around the aboral edge of the upper arm-plates are dis- 

 tinctive characters, which are, to a certain extent, suggestive 

 of Ophiolepian and Ophiopholian affinities. Nevertheless the 

 dental apparatus does not resemble that of these last genera. 

 There is much in the form under consideration which recalls the 

 shape and spinulation of Ophionyx, M. & T. ; but the absence of 

 tooth-papilla? and the presence of accessory plates to, and 



LINN. JOURN. — ZOOLOGY, VOL. XT. 6 



