A treatise on malacology; or, Shells and shell fish . oluteline of demarcation between Iridea and Mysca, whichis contrary to nature ; but the facts now stated willenable any one to discriminate the two types. Thenext sub-genus is Lamarcks Castalia, of which butone species is generally known. Reasoning from ana-logy, it follows Iridea ; but if so, the minor types ofconnection are wanting. It is a cockle-shaped shell, nearly equilateral, and59 bears a strong resem-blance to JEglia cune-ata. From this rareand somewhat isolatedtype the transition toHyria (fig. 5^.) is ren-dered easy and naturalby
A treatise on malacology; or, Shells and shell fish . oluteline of demarcation between Iridea and Mysca, whichis contrary to nature ; but the facts now stated willenable any one to discriminate the two types. Thenext sub-genus is Lamarcks Castalia, of which butone species is generally known. Reasoning from ana-logy, it follows Iridea ; but if so, the minor types ofconnection are wanting. It is a cockle-shaped shell, nearly equilateral, and59 bears a strong resem-blance to JEglia cune-ata. From this rareand somewhat isolatedtype the transition toHyria (fig. 5^.) is ren-dered easy and naturalby means of Hyria cor-rugata Lam. ; and Hy-ria elongata indicates a passage to that elongated formwhich has not yet been discovered, and which mustrepresent either Alasmodon or Iridina^ Such a shellwe remember to have once seen at Kings Auction-rooms, but by some accident neglected to take notes, orto secure the specimen. In the sub-genus Naia, whichwe arrange under Castalia, we have a form connectingthe C. cordata* with Iridea. AV^e have before us six. * I use the prior specific name of Ilumplircy rather than Lamarcksambigua, which throws an unnecessary tioubt on its being a species. CHAP. X. HYRIN^ AND UNIONINiE. Og^ species, four of which are from India_, and two fromAustralia. They are short, roundly oval shells, withthe umbones well defined, and placed tow^ards themiddle: from this results their peculiar character. Thelateral teeth are short, and not a great deal longer thanthe cardinal teeth ; these latter being strong and thick,without being short: they are much crenated, yetwithout any ridge ; so that they have the appearance ofbeing broken off. Their immediate affinity to Trideais proved by the Naia elongata, from New Holland,having the form of one type, and the teeth of the interesting species, once the property of admiralBligh, was purchased by us at his sale. The pecu-liarities of Lamarcks Unio Australis (^Hyridella Sw.),and its affinity to Iridea, lead us t
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectmollusks, bookyear184
