948 RECORD OF CURRENT RESEARCHES RELATING TO 



as to the nature of the solid cones he is not yet prepared to settle. 

 Are they crystalline lenses or only analogous organs ? Can the horse- 

 shoe crab distinguish objects ? He doubts if its eyes enable it to 

 more than distinguish between the light and darkness. 



Eye of Trilobites.* — Dr. Packard has also investigated the 

 internal structure of the hard parts of the eye of Trilobites ; only the 

 entire eye, the external anatomy of the cornea, and the form and 

 number of the facets having been previously described and figured by 

 Burmeister, Barrande, and others. 



From the facts presented it would seem evident that the hard 

 parts of the eye of the Trilobites and of Limuliis are, throughout, 

 identical. The nature of the soft parts will, as a matter of course, 

 always remain problematical, unless the dark line which seems to 

 run across from one lens to another really represents the outer 

 edge of the pignient of the retina ; but however this may be, judging 

 by the identity in structure of the solid parts, we have, reasoning 

 by analogy, good evidence that most probably the eye of the Trilo- 

 bites had a retinal mass like that of Limuhis, and that the numerous 

 small branches of the long, slender, optic nerve (for such it must 

 have been) impinged on the ends of the corneal lenses. It has 

 been shown by Grenacher and the author, that the eye of Limulus 

 is constructed on a totally different plan from that of other Arthro- 

 pods ; and he now feels authorized in claiming that the Trilobite's eye 

 was organized on the same plan as that of Limulus ; and thus when 

 we add the close resemblance in the larval forms, in the general 

 anatomy of the body-segments, and the fact demcmstrated by Mr. 

 Walcott that the Trilobites had jointed round limbs (and probably 

 membranous ones), we are led to believe that the two groups of 

 Merostomata and Trilobites are subdivisions or orders of one and 

 the same subclass of Crustacea, for which he previously proposed the 

 term PalfBOcarida. 



New Entomostraeon from Afghanistan.f — Dr. F. Day describes 

 (from a collection made by Dr. Duke in Afghanistan) a new entomos- 

 traeon — Ajnis dukianus — captured in a pond near Kelat in 1877. 



Superiorly the general colour of the carapace is olive, the spinous 

 projections sienna, and the body and tail dull yellow. The largest 

 examjjle is 1 • 4 inch long, • 6 inch in width, while the caudal aj)pen- 

 dages are • 7 inch in length. The caudal portion of the body is 

 twice as long as the carapace. The segments of the body have each a 

 transverse row of from six to eight short, spinous elevations directed 

 backwards, the lateral spine being that most developed. The joints of 

 the caudal appendage are similarly, but less strongly armed, to those of 

 the body. The entire extent of the semilunar notch at the posterior 

 extremity of the carapace is armed with very fine and short needle- 

 like points, all being of about the same size ; while under the Micro- 

 scope the hind portion of the carapace's outer edge is also seen to bo 

 minutely and evenly armed with fine points. 



* ' Am. Natural.,' xiv. (1880) p. 503. (1 fls^s.) 

 t ' rroc. Zool. Soc. Lond.,' 1880, p. 392. (1 fig.) 



