东海大陆架掌苔虫属一新种

掌苔虫属(Genus Kinetoskias Danielsen,1868)隶于唇口目、无囊亚目、双胞科(Cheilostomata, Anasca, Bicellariellidae),除南极海域、地中海、加勒比海未见报道外,各地都有记录,但多数种类在北极海域分布较广(Kluge,1953)。掌苔虫系深海类型,有的种能栖息在水深4670米的深海海底。掌苔虫的个虫系草苔虫型(Bugula-type),与草苔虫不同处是个虫始端不分叉。掌苔虫和茎苔虫(Caulibugula Verrill,1900)的群体都由一根长柄和分枝部分构成,但掌苔虫的长柄为膜质;无任何钙质沉淀,仅由一空个虫(keno zooid)构成,而茎苔虫的长柄分节,由许多空个虫构成,往往有钙质加厚,因而两属极易区分。掌苔虫群体分枝的分歧方式属于Harmer的模式7(见Harmer，1923:326,pl,16,fig.7)，即双列分枝在分歧时,两个内个虫(inner zooids)F和G分别由轴个虫(axillary zooid)E相连接,轴个虫产个虫F和G,它伸到与个虫A对应一侧分枝的始端,个虫B不参与个虫数目的复分(图2)。 掌苔虫虽系深海类型,但有的种深度分布范围很广,如Kinetoskias arborescens栖息在水深19-1229米,K.smitti分布在水深65-1210米,S. mitsukurii则分布在水深20-3400米(Kuge1953、1962；Menzies1963)。 掌苔虫的群体借助于膜质长柄插入海底淤泥,由长柄始端分出的微细附根附着在砂粒等基质上。个虫由于特殊的个虫牵引肌(flexor: Zooidal muscles)的伸縮彼此间能活动。鸟头体皆侧位,都长在个虫自由缘上,或位于个虫中点(mid-point)。或位于中点以上(cephlad of the mid-point),或位于中点以下(caudad to the mid-point);有的种鸟头体长在特殊阶梯状突起(step-like process)上,但有些种类无此阶梯状突起。

A NEW SPECIES OF THE GENUS KINETOSKIAS DANIELLSEN COLLECTED FROM THE CONTINENTAL SHELF OF THE EAST CHINA SEA

Kinestoskias oblongata sp: nov.(text-figs. 1-6) Colony consists of a tubular stalk and a typical palm-like branch whose end is not curved. The branch consists of two rows of alternative zooids. The tubular stalk is 80 mm. long, and is a kenozooid with thin membranous wall, uniformly wide throughout the portion above the proximal end. From the base of the stalk are given off minute rootlets. At the distal end of the stalk, near the primary zooid of the proximal end of the branch, the stalk lumen is expanded into membranous aperture, a portion of the distal end of which is raised toward the frontal surface, on the dorsal surface. The wall of the stalk is arched. It is to this are-like area that a large pyriform structure is attached. The attachment plane of this structure has the same curvature as that of the tubular wall. The structure is broader basally than distally and is connected with the proximal end of the primary alternative zooid of the palm-like branch by a chitinous joint. By another such joint the proximal end of the second alternative zooid in the proximal end of the branch is also connected with a small conical structure attached on the disto-dorsal edge of the above-mentioned arc-like area. The fifth alternatively arranged zooid distal to the stalk takes part in the bifurcation. Zooids are oblong, narrower proximally, their distal end sloping slightly and obliquely toward outer distal corner, usually with or occasionally without a small spine(not jointed at the base),inner distal margin round; their dorsal surface is convex and smooth.The outer proximal side of each polypide has a columella-like process, to which tip are attached the muscles; musele fibres are rather strong, penetrating into the lateral and dorsal wall of the polypide which is large and occupying about the anterior or more than half the length of the zooid. The lophophore is small, tentacles about 24 in number. Avieularia are small, attached to the outer side of the middle of the proximal half in a zooid. They are of the elongated type, their base is narrow, their profile is nearly straight, their rostrum is short and inconspicuously hooked, their mandible is simple and triangular. Usually most of the avicularia extend to the frontal surface of the zooids. Ovicells are broader than long, attached to inner distal corner, obliquely covering the surface of the neighbouring zooids. The eetooecium is separated from the entooecium by a space. The entozooecium is marked by a longitudinal line or slit perpendicular to the ooepore, and by many stripes parallel with the ooepore. This new species bears a resemblance to Kinetoskias elongata Harmer 1926. In the. latter species the zooids are elongated, the avicularia are located cephalad of the midpoint of a zooid, the ovicells are marked only by the radiating lines. In this new species the zooids are oblong, the avicularia are located caudad to the mid-point of a zooid and the ovicells have peculiar stripes.