T. V. JEolmes—Oii DeneJioles and Bell Pits. 447 



I know. The general similarity, however, between the eye-line 

 and eye-spot of Harpes and these structures in the larval Trinucleus 

 is in favour of regarding the latter as organs of sight. From the 

 resemblance of the tubercle on the glabella to those on the cheeks, 

 we ought probably to regard it as possessing likewise a visual 

 function. 



The other two genera, Ampyx and Dionide, which are placed in 

 the family Trinucleidge, have no eyes at any stage of their develop- 

 ment, so far as is known, and they show the typical Hypoparian 

 characters. In neither genus have we any reason to suspect 

 degeneration. The genus Ampyx displays the intermediate stage 

 in the migration of the free cheeks from the ventral to the dorsal 

 surface of the cephalon. (Ehlert's ^ view that the marginal position 

 of the suture of Trinucleus, Ampyx, and Harpes is the result of 

 the displacement of the normal facial suture, and is therefore 

 a secondary character and less primitive than the dorsal position, 

 is opposed to all our knowledge of the ontogeny and phylogeny of 

 the trilobite. 



There are two genera, Salteria and Endymionia, with doubtful 

 affinities, which are usually placed in the family Trinucleidse. The 

 genus Salteria (Wyv. Thomson)^ possesses linear fi'ee cheeks which 

 ai-e supposed to bear eyes ; but the evidence for their presence is 

 weak,^ and it is most probable that the genus is really blind. The 

 other genus, Endymionia (Billings),* has only been found in America, 

 and is considered to be allied to Trinucleus and Ampyx, and, so far 

 as is known, it possesses no organs of vision. 



(To be continued.) 



IV. — On Deneholes and Bell Pits. 

 By T. V. Holmes, F.G.S., Hon. Sec. Anthrop. Inst. 



IN the Geological Magazine for July appears an article by 

 Mr. Charles Dawson on Ancient and Modern Dene Holes. As 

 Mr. Dawson mentions Essex deneholes, and comes to conclusions 

 contrary to those arrived at by Mr. Cole and myself, the authors of 

 the Eeport of the Essex Field Club on the Deneholes of Hangman's 

 Wood, near Grays Thurrock,^ I shall be glad to be allowed space 



1 D. P. (Ehlert, Bull. Soc. Geol. France, vol. xxiii (1895), p. 319. 



2 Mem. Geol. Surv., dec. xi, No. 6 (1864), p. 1. 



* Nicholson and Etheridge, Mon. Sil. Foss. Girvan, fasc. 2, p. 199. 



* Geol. Canada: Pal. Foss. (1865), vol. i, pp. 33 and 281. 



* Report on the Denehole Exploration at Hangman's Wood, Grays, 1884 and 1887: 

 hy T. V. Holmes and W. Cole (with three coloured plates and other illustrations). 



Note on the Bones found in the Deneholes in Hangman's Wood : by E. T. Newton. 

 Note on a fragment of Millstone from a Denehole : by F. W. Eudler. 

 On Chalk Wells : by F. J. Bennett. 



Note on some Pits near Chipping Norton, Oxfordshire : by H. B. Woodward. 

 Ensilage, or Preserving Grain in Pits : by F. C. J. Spurrell. 

 {Essex Naturalist, December, 1887.) 



