DESCRIPTION OF PLATES, 27, 28. 667 



b, single medial nerve, running to the great transverse 



muscle, extending across the upper part of the stomach. 



c, collar-nerve or chord, uniting the infra- and supra-ceso- 



phageal ganglions. 



d, great splanchnic nerve, here spread laterally out, but 



properly running along the sides of the upper part of 

 the prosoma, and therefore under the collar-nerve; 

 d' y plexus by which this nerve is connected with the 

 supra-splanchnic nerve, e. 



e, supra-splanchnic nerve, rising from the collar, almost in 



contact with the supra-cesophageal ganglion ; e', small 



nerve rising from the end of the supra-cesophageal 



ganglion, and running to the adductor and surrounding 



muscles. 

 /,/, pair of great nerves (antennular), distributed over the 



sack and shell. 

 g, chord (in appearance single), uniting the supra-cesophageal 



ganglion with the first (c), or ophthalmic ganglion. 

 h, small medial nerve, running to near the adductor muscle. 

 i, nerve supposed to run from the ophthalmic ganglion to the 



eve. 

 k, small nerve, rising from the main ganglion (a), between 



r a and r 2 , or the nerves running to the first and second 



pairs of cirri. 

 (£, position of the oesophagus. 

 r \ nerve entering the first cirrus. 

 r 2 , r 3 , r 4 , r 5 , r 6 , nerves entering the five succeeding 



pairs of cirri. 

 s, nerve entering the probosciformed penis. 



2, nervous system of Balanus tintinnabulum ; letters of reference 



as in fig. 1. 



3, acoustic sack of Balanus tintinnabulum. 



4, ,, ,, Coronida diadema. 



5, eye of Balanus tintinnabulum ; i, nerve coming from the 



ophthalmic ganglion ; d, eye itself. 



PLATE 28. 



Cementing Apparatus. 



Fig. 1 a, Basal membrane, with the cementing apparatus, of Coronida 

 balcenaris ; a small portion of the parietal membrane, p p p, 

 which coats the folded shelly walls, is left adherent to the 

 basal membrane. 

 by the circumferential slip (shaded more darkly than the rest to 

 catch the eye), separating the basal from the parietal mem- 

 brane. 

 c' c', slips of basal membrane, formed at each period of growth, 

 and overlapping each other. 



