论Oysters

ON OYSTERS

林奈于1758年建立了Ostrea (s.l.)属。此后的两百多年中经拉马克(Lamark)、杜威尔(Douville)、乌雅洛夫(Vyalov)、斯坦兹尔(Stenzel)等许多学者的深入研究,不断修正、补充与完善,原来的Oatrea (s.l.)属现已扩展为牡蛎超科(SuperfamilyOstreacea),人们通常称之为Oysters(牡蛎类)。目前对Oysters的特征、分类、生态、起源、演化等方面的认识正不断深化,但仍存在不少分歧。

Oysters are members of the class Bivalvia,subclass Pteriomorphia,order Pterioida, Suborder Ostreina, superfamily Ostreacea. Many authors usually look upon the characters and geologic range of Oysters and the Ostrea (s.s.) as the same. It is neccessary to clarify some obscure views in order to avoid the confusion. In this paper we try to express some opinions on this problem. In it we also record Laevostrea,a new genus of oysters collected from the Upper Jurassic in Mishan, Heilongjiang.Its diagnosis is described as follows:Suborder Ostreina Ferussac,1822Superfamily Ostreacea Rafinesque,1815 Family Ostreidae Rafinesque,1815Subfamily Ostreinae Rafinesque, 1815Genus Laevosfrea(gen.nov.) Type species. "Ostrea"intermedia Yao(MS)Diagnosis: Shell medium-sized to large,mostly elongateorbicular,left valve more convex than right valve, umbonal cavity shallow. Adductor-muscle imprint reniform. The internal margins of both valves smooth,without chomata. Both valves covered with irregular concentric wrinkles and growth. lines.Remarks: The new genus is similar to Ostrea (s.s.) with smooth internal margins and adductor-muscle imprint reniform, but differs from the latter in shape and ornaments of shell. This new genus also much resembles Liostrea, which is known from the Upper Triassic to Jurassic and is classified into the subfamily Gryphaeinae , in both valves covered with concentric wrinlkes and growth lines, with shallow umbonal cavity and absence of chomata,but Liostrea differs from Laevostrea in adductor-muscle imprint orbicular and near the hinge margin.Several species of Liostrea which have been described from Hulin County, the east of Heilongjiang Province may be included in this new genus,owing to their large, elongate-orbicular adductor-muscle imprint and valves covered with irregular concentric lines.