294 Frederick Ghapman : 



Fam. Trinucleidae. 



Genus Ampyx, Dalmau. 



AmjDyx paj'vulus, Forbes, var. jikaensis, var. nov. 

 PI. LXI., Figs. 1, 2). 



Description of the Victorian variety. — 



The holotype selected is a nearly entire carapace, but without 

 genal and frontal spines ; whilst on the same slab are several 

 impressions of the thorax and pygidium of the same form. 

 Another specimen, from Mr. Spry's collection, shows a faint 

 impression of the base of a frontal spine. In its subcircular 

 <iontour, strongly convex and oval glabella, with deep sulci 

 separating it from the cheeks, this variety closely resembles 

 Forbes' species^. The axis, however, is somewhat narrower in 

 the Australian variety, being about one-fourth of the entire 

 width of the carapace at the widest part of the thorax. The 

 pygidium differs also from the British specimens in being 

 slightly shorter in proportion to breadth. The thoracic seg- 

 ments, as in the type species, number five. 



Dimeiisions. Length of carapace from anterior border of 

 glabella to end of pygidium, 5 mm. ; greatest Avidth, 4.5 mm. ; 

 length of cephalon, 2.25 mm. ; length of thorax, 2 mm. ; length 

 of pygidium, 0.75 mm. 



Observations. — In Britain A. parvulus is recorded from the 

 caradoc series (upper ordovician) and from the wenlock shale 

 ^upper Silurian).'^ 



The varietal name jikatnsis, attached to the Australian 

 .specimens is derived from the parish name of the locality where 

 it is found, Jika-jika. 



This appears to be the first occurrence of the genus in Aus- 

 tralia. 



Occurrence. — In black, micaceous shale of silurian (mel- 

 bournian) age. Moonee Ponds Creek, near Melbourne. Found 

 and presented by Mr. J. Sidney Green. Mr. F. P. Spry, who 



1 Ampyx parimlus, Forbes. Mem. (.'eol. Sur\ . Gt. IJrit., vol ii., pt. 1. 1S48, p. HoO, pi. 

 :\.,fi,<?s. 1, la, 2, 2a, 3. 



2 See Etheridge, Robt., Foss. Biit. \<U., vol. i., I'alaeo/oic, 1888, p. 40. 



