Prof. P. M. Duncan on the Salenidae. 65 



marked generative pore, and greatly resembles the others 

 already noticed. It has a pit in the midst of its suture with 

 the preanal, and another in the suture with the posterior plate. 

 In all these plates there are pits at the angles also. 



The preanal plate is six-sided and smaller than the others ; 

 it rises to a rim-edge with a slight extra elevation where it 

 bounds the anus ; and this edge is concave and almost angular. 

 The sutural lines in contact with the anal rim are the shortest ; 

 and the others are nearly equal to each other in length. All 

 except the two shortest have an extra pit in the midst. 



The posterior plate has a rim-edge bounding the anal orifice ; 

 and the pore is situated where the ridge begins to rise from 

 the body of the plate, or in the ridge itself Resembling the 

 anterior plates in general configuration, it is broader at its base, 

 where it conforms to the figure of the right posterior plate, 

 with which it is in lateral contact to the right. The right 

 posterior plate resembles in general outline the left posterior, 

 but it has the same structm'e as the posterior internally ; the 

 rim is stout, and the pore is either in it or at its base. In some 

 of the specimens this plate is the smallest. 



The ocular plates are well developed and are subequal. The 

 external margin is long trilobate, and, on the whole, straight ; 

 the central lobe is often incised, and the outer ones slightly 

 pointed. The outer edge is slightly raised and hides the 

 ocular pore ; and the edge forms a slight rim to the whole 

 plate, so that there is a hollow on the top and internal to the 

 margin. There are four sutures in relation to each plate, and 

 two short edges which unite the marginal edge with the gene- 

 rative plates. Internally the plates are pointed and arise in 

 the sutural angles of the generative plates. The right poste- 

 rior ocular plate has its internal point close to the edge of the 

 anus, the rim being traversed by a very short suture between 

 the generative plates. Hence this ocular plate comes close to 

 but does not enter into the composition of the rim. The 

 sutures which are in relation with the ocular plates, except 

 the last noticed, point to a spot on the preanal disk, very 

 slightly posterior to a line drawn from one posterior poriferous 

 zone of the antero-lateral ambulacrum to the other. The 

 external straight edge of the ocular plate is in advance of the 

 angular end of the generative plates on the pentagonal out- 

 line of the disk. The generative pores are surmounted by a 

 rim. 



The ornamentation is stated by Prof. Tate to be like 

 shagreen ; and this fine irregular microscopic structure is well 

 seen here and there. It is very irregular and minute, and 

 covers the small rounded and more or less eccentric rings of illr- 



Ann. & Mag. X. Hist. Ser. 5. Vol. ii. 5 



