MOLLUSCOIDA. 41 



the west, and the extreme north and soutli, as shown in tlie 

 valuable catalogues of Messrs. Alder, Couch, Hincks, and 

 Norman. Many species will doubtless yet be found at St. 

 Andrews — though at present they appear to be confined to the 

 other areas, which have been more thoroughly investigated by 

 observers specially skilled in this department. Bicellaria 

 ciliata and Bugula purpurotincta seem to be more common at 

 St. Andrews than in Shetland, the latter fonn being especially 

 abundant and fine, and apparently taking the place of the 

 Ti. flumosa of the southern shores ; Menipea ternata and 

 Bugula Murrayana are likewise in considerable profusion and 

 in fine condition ; while the southern Flaatra cJmrtacea is 

 wholly absent. Tlie species of the Membraniporida;, perliaps, 

 are more abundant in Shetland ; and Xh^Lepraliae are decidedly 

 more numerous there and in the extreme south. Amongst the 

 more conspicuous forms we notice the entire absence of Lepralia 

 Pallasiana, so common in the extreme west and south, and 

 of the characteristic L. innominata and L. figularis of the 

 latter. The Celleporidse are abundant, but the species are 

 few. Cellepora avicularis is exceptionally rich, according to 

 Mr. Hincks ; and the same high authority in this department 

 states that the sole specimen of Eschara Skenei is fine. 



The Cyclostomatous forms are not numerous ; but all the 

 examples are abundant ; and the same may be said of the 

 Ctenostomata. The late Dr. John Eeid mentions Vesicularia 

 spinosa as growing near low-water mark ; but I have not been 

 successful in finding it. The Zetlandic Hornera and the rich 

 tufts of Amathia lendigera, so plentiful in the south, , are 

 altogether absent. 



On the whole it would appear that the Hebridean, Zetlandic, 

 and southern waters furnish a richer field for the Polyzoa than 

 our eastern shores, not only as regards the number of species, 

 but the condition and size of the specimens. I need only 

 allude, for instance, to the luxuriance of the branching 

 Celleporid^ and Eeteporaj of the Hebrides and Shetland, and 

 the extraordinary beauty and profusion of the Escharidse and 

 Lepraliffi, and indeed of the whole group, in the extreme south 

 and in the Channel Islands, both between tide-marks and on 

 the shell-banks around. 



G 



