74 Mr. C. Spence Bate oyi a new Genus of Mncrura. 



wliicli have*been transferred into the ' Challenger' Keport on 

 the Crustacea Macrura, p. 112, ^^Eryon was probably not blind, 

 for the eye-stalks have been found in several specimens." 



On the other hand, Dr. Woodward, of the Britisli Museum, 

 who as a geologist has given much attention to this group of 

 Crustacea, says that the eye " has never been positively 

 determined," and he has restored a specimen with these organs 

 present. I have never seen a specimen, neither, I believe, has 

 any ever been found in which the ophthalmus is undoubtedly 

 preserved. 



In Eryon Brodiei the orbit is preserved and shown to be 

 moderately deep, and the latero-anterior angle is well ad- 

 vanced. It is the same, but in a rather less marked condition, 

 in Erynn ivilmcotensis, while in Eryon Moorei and Eryon 

 crassichelcs both orbital notch and antennal anffle arc reduced 

 to a mmnnum. 



In Arcluvastacus Willemcesii the latero-anterior angle of the 

 carapace is so well developed as to produce a well-formed but 

 shallow orbital notch in the frontal margin of the carapace in 

 position corresponding with those found in the recent genera, 

 but less excavate and characteristic. In this unique fossil 

 the ophthalmopoda are not preserved, but the form of the orbit 

 is suggestive of the existence of such an organ. 



From the Upper Lias of Calvados M. Mori(5re described * 

 a species under the name of Eryon calvadosii, in which the 

 orbits for the reception of the organs of vision are well pre- 

 served, and the specimen has the appearance of having had the 

 ophthalmopoda broken off and retained in the lost matrix. 



If we now turn to the specimen before us we find that the 

 organs of vision are present in a peculiar and well-developed 

 form. The ophthalmus is projected upon an elongated and 

 slender stalk, and is capable of being bent considerably on 

 itself; and both articulations possess considerable mobile 

 power, so much so that the ophthalmus is capable of being 

 bent beneath the frontal margin and hidden from view. But 

 although it is not visible when inspected on the dorsal sur- 

 face, it is so placed that it is capable of seeing through 

 the curved or hollow space that exists on the outer side 

 beneath the antero-frontal angle of the carapace ; but when 

 the animal wills it is capable of being projected forwards, 

 and when advanced the peduncles may be seen very much like 

 those shown in Eryon Cuviertj as figured by Desraarest 

 and shown in our woodcut on page 73. 



The first pair of antennas exhibit a peculiarity at variance 



* Bull. Soc. Liun. de Normaud. S(5r. 3, torn. vii. pp. 1-10, pis. i.-iii, 

 (1883). 



