REPORT ON THE CRUSTACEA MACRURA. XV 



stage, a fact that is apparent in nearly all purblind species and is especially noticeable 

 in Alpheus and Willemcesia, as may be seen by reference to PI. LXXXIX. fig. 4, and 

 PL XX. fig. 2. 



In the several forms classified under the generic name of Eryon, the organs of vision 

 appear to have become degenerated. In most specimens of the various fossil species, no 

 trace of eyes has been detected. In the original specimens, as figured by Desmarest in 

 his Considerations generates sur la classe des Crustaces, PL XXXIV. fig. 3, part of a 

 Particulate appendage is present on the frontal margin on each side, beyond the second 

 pair of antennae. If, as is possible, these are the remnants of the appendages that 

 supported the eyes, I think we must come to the conclusion that they were pro- 

 jected at the extremity of a long or short pedicle. 



In a specimen unearthed in 1882 1 from the Upper Lias strata of Calvados and 

 described by M. Moriere, the general features bear a resemblance to the Willemcesia of 



Fig. II. — Enjon calvadosii, after M. Moriere. Reduced one-half. 



recent seas, excepting that in the Calvados specimen large organs of vision are 

 conspicuous, or rather, 1 should say, that the orbits for the reception of the organs of 

 vision are well preserved, and as M. Moriere says of his specimen that " On apercoit 

 des pedoncles oculaires." These are situated on the fronto-lateral margins of the carapace, 

 on the outer side of the second pair of antennae, somewhat after the manner occasionally 

 seen in some of the Palinuridse and some of the Scyllaridse ; but it is more common 

 among the Brachyura than the Macrura. The eyes are similarly situated, but not so 

 largely developed in the Willemcesia group, in which they are moreover in a more marked 

 state of degradation. In Willemcesia and its congeners, the ophthalmopoda are deeply 



1 Did!. Sue. Linne'nne de Normandie, sir. 3, torn. vii. p. 1, 10, pis. i., iii., 1883. 



