. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 522 A. H. SCHELTEMA Description External morphology. Chevroderma whitlatchi is small and opaque; in many con- tracted specimens, the trunk is broadest posteriorly, producing a translucent hump at the juncture with the posterium. Spicules of the anterior half of the trunk, when it is contracted, assume an upright position; further posteriorly they meet at a distinct angle with the tips overlapped along the dorsal midline (Fig. 3H). They are arranged parallel to the body along the dorsal side of the posterium. Total length ave
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 522 A. H. SCHELTEMA Description External morphology. Chevroderma whitlatchi is small and opaque; in many con- tracted specimens, the trunk is broadest posteriorly, producing a translucent hump at the juncture with the posterium. Spicules of the anterior half of the trunk, when it is contracted, assume an upright position; further posteriorly they meet at a distinct angle with the tips overlapped along the dorsal midline (Fig. 3H). They are arranged parallel to the body along the dorsal side of the posterium. Total length averages and mm in two populations (Table VI), with greatest length mm. Trunk di- ameter averages mm and ranges up to mm. The posterium is long, two-fifths total length, and averages mm in length by mm in diameter, with greatest dimensions and mm, respectively; posterium to trunk length index averages and in the two populations, with a large range, to The two pop- ulations were not significantly different in any of five body measurements (Table VI). The oral shield spicules are small but distinct; the oral shield is large (Fig. 3K). Holotype: Total length mm; trunk by mm; posterium by mm; index of posterium to trunk Oral shield by mm; index of oral shield to trunk diameter Spicules: The blade of trunk spicules is short relative to the base and narrow, abruptly tapering from a distinct waist to a usually pointed apex (Figs. 5E, 13c H, A). The blade is bent outwards from the body wall and usually bears a medial ridge (juvenile) or distinct broad keel. The base is narrow and rotated about the long axis. The sides of the base are usually nearly straight and tapered proximally, so that the base is widest at the waist. Trunk spicules are thickest at, or just distal to, the waist. The longitudinal groove seldom extends beyond the base and may be very faint. Great- est spicule length is abou
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
