414 



PEOE. P. M. DUNCAN ON ECHINOIDEA 



Ternnopleurus and of Temnechinus was published, which enables the 

 genera to be well separated. D'Archiac and Haime * passed very 

 abruptly over the claims of Temnechinus, Porbes, and placed all the 

 beautiful forms they discovered amongst the Sind Tertiaries in the 

 genus Ternnopleurus. They should, however, have been placed in 

 Temnechinus. But associated with these forms were others which 

 had a raised costulate ornamentation only, without furrowing of 

 sutures or the presence of true and false pits. By the light of the 

 morphological investigations, these species were removed from Tern- 

 nopleurus, Agass., and Temnechinus, Forbes, and associated with the 

 genera Piety opleurus, Arachniopleurus, Dune. & Sladen, &c, and it 

 is in their neighbourhood that the species formerly named Temne- 

 chinus lineatus, nob., must come. In fact it is correct, from what 

 is now known, to distinguish three alliances of genera, the Temno- 

 pleuroid, the Temnechinoid, and the Dictyopleuroid, and the species 

 under consideration must come within the latter group. 



Up to the present time no true Temnopleurus or true Temnechinus 

 has been found in the Australian Tertiaries. 



Laube f discovered and described an Echinoid which, unfortunately, 

 had no apical system ; but the basal and radial plates had left their 

 impressions on the test surrounding the periproct. The ornamental 

 characters associate this form with the Tertiary Dictyopleuroids of 

 Sind and Kach, but there are more than specific distinctions between 

 Paradox echinus novus, Laube, and the costulated form called Temne- 

 chinus lineatus. 



It is, however, evident that the apical system of the form which 

 was termed Temnechinus lineatus, and which it is now proposed 

 should enter a new genus, Ortholophus, is small, and not one half of 

 the dimensions of that of Paradoxecliinus, the measurement being 

 made across the vacant spaces and as far as any evidence of former 

 structure occurs. 



The so-called Temnechinus had not the elongated periproct of the 

 genus Pictyopleurus and of Paradoxechinus, and no radial plate 

 entered the periproctal ring as in those genera. It is therefore 

 necessary to define a genus for Ihe species, which has a small apical 

 system and a remarkable straight and crowded transverse costulation 

 of the test. 



Genus Oetholophus, gen. nov. 



The test is small, low, more or less pentagonal in marginal outline, 

 subcorneal above the tumid ambitus. Apical system (wanting). Peri- 

 proct small and circular, Ambulacra one half of the width of an inter- 

 radium at the ambitus, straight, with slightly sunken poriferous 

 zones ; pairs in ill-defined triplets nearly in straight series, appear-! 

 ing on the edges of transverse costae. Compound plates with a centra) 

 demiplate, the others primaries. A vertical row of small imperforate! 

 non-crenulate primary tubercles is close to the poriferous zone, ancj 



* Anim. Toss, de l'lnde, p. 202. 



t Laube, Sitzungsb. Akad. Wiss. Wien, Bd. lix. p. 186.. fig. 2 (1869). 



