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Show 1906.] ON THE ASCIDIANS OF CAFE VERDE ISLAND. 903 bases near the skin. A similar combination of procryptic coloration when at rest and of aposematic coloration when disturbed, is shown by the large Indian Mygaloid Spider Pcecilotheria and by many of the Lycosidae *. The above-mentioned facts and theories are based upon observations of the Porcupines that have lived during the past three years in the Society's Gardens. Dr. C. G. Seligmann, F.Z.S., exhibited two skulls of male Domestic Sheep, and made the following remarks :-The two heads shown contrast the form of skull of the normal ram of the Herd wick breed (in which only the males have horns) and a ram of the same age and breed castrated in infancy. The skull of the castrated sheep or wether is less rugged and the bones thinner, but besides such general differences and the obvious absence of horns the plane of the os frontis is continued backwards behind the orbits at a very obtuse angle, in the skull of the normal ram the plane of the frontal behind the orbit lies almost at right angles with the interorbital portion of the bone, the horn-cores arising from the upper or horizontal area. Although the skull generally is thicker in the normal ram than in the wether, this alone does not account for the difference in external form, seeing that the cranial cavity presents a corresponding extension in the frontal region. It is worth noting that the conformation of the skull of the castrated animal resembles that of the hornless ewe of the breed. The following papers were read :- 1. On Collections of the Cape Yerde Island Marine Fauna, made by Cyril Crossland, M .A . (Cantab.), B.Sc. (Lond.), F.Z.S., of St. Andrews University, July to September 1904.- T h e A s c id ia n s . By J o h n R e n n ie , D.Sc., and H a r r y W is em a n , M.A., B.Sc., University of Aberdeen, t [Received October 12, 1900.] (Plates LXIY. & LXY.t) This memoir deals with the Ascidians collected by Mr. Crossland at Cape Yerde in the year 1904. Although a fairly abundant supply of material was secured, it has not proved particularly rich in species. In all, examples of only ten forms were collected, two of which appear to be new to science. Notes regarding localities are meagre ; most of the specimens appear to have been obtained at Mattiota, St. Yincent Harbour. * See Pocock, Ann. Mag. Nat. Hist. (7) iii. p. 84, 1899. f The expenses of Mr. Crossland's collecting trip were borne by the Carnegie Trustees. + For explanation of the Plates see p. 910. P roc. Z o o l . Soc.-1906, No. LX. 60 |