156 THE PROCEEDINGS OF THE LINNEAN SOCIETY 



Genus 3. — Parasalenia, A. Agassiz, 1863. 

 Arcs of pores of three pairs only, anal system very small, 

 closed by only four plates. Buccal membrane carrying minute 

 spines. 



Parasalenia gratiosa, A. Ag. 



Very like B. lacunter, and generally associated with it. The 

 spines are often extremely alike. I have met with no well 

 authenticated case of its occurrence in Australia. 



Genus 4. — Stomopneustes, Agas, 1841. 



Test nearly circular, axis very slightly oblique. Actinal surface 



fiat ; actinosome small, cuts scarcely marked, pores in three 



irregular vertical lines. Two principal rows of tubercles in both 



areas, but the I. area almost filled up with somewhat smaller 



ones. Spines long, stout, and finely striated. 



Stomopneustes variolaris, Lamk. 



This species (the only one of the genus) is easily known by 

 the continuous groove extending along the vertical suture in 

 median I. space. The specimen in the Sydney Museum is very 

 much larger than any of the dimensions given by Agassiz, as 

 the following dimensions will show : — Diam. 102, alt. 52, 

 abactinal system 15, actinosome 25 (exclusive of cuts), spines 

 from 45 to 62, and about 4 mil. at base. It is probable that this 

 specimen comes from North Australia, but the precise looality is 

 unknown. 



Genus 5. — Strongylocentrotus, Brandt, 1835. 



This includes all species having a somewhat circular or sub- 

 pentagonal, regularly arched, or slightly depressed test, with 

 smooth, imperforate, not crenulate tubercles of unequal sizes, 

 forming primary and secondary vertical rows. Pores arranged 

 in arcs of at least four or five pairs. Actinosome decagonal, very 

 slight cuts, buccal membrane bare, spines moderately slender, 

 longitudinally striated, longer proportionately than those of true 

 Echinus, and more slender than Sphcerechinus. 



