Adelatelecrinus new genus

Atelecrinus: AH Clark 1912: 152.— Hartlaub 1912:480 –481 (part).—AH Clark 1918:262, 266–268 (part).— Clark and Clark 1967:817 –819 (part).

Diagnosis. A genus of Atelecrinidae with centrodorsal hollow and thin-walled, closely joined to basal ring or slightly separated interradially by narrow gap or slit; central cavity diameter ≥0.6 of basal diameter; adoral rim of centrodorsal with 5 hollow, interradial buttresses that open adorally as deep, ring-shaped pits (Figure 7 d). Cirrus sockets in 10 columns with moderately developed aborally-projecting lateral fulcral tubercles triangular in side view; cirri (when known) tapering to a point with no opposing spine. Externally visible portion of each basal flat or slightly arched, weakly swollen interradially if at all, with lateral portions parallel-sided or tapering, and ends contiguous midradially (Figures 7 a, 8); sometimes reduced, triangular and separated midradially (Figure 7 b, c). Aboral surface of basals with featureless, central depression, and with adorally curved and distally expanded pair of interior projections (Figure 7 e). Radial cavity with delicate aboral calcareous deposit. Most proximal pinnule on IIbr15–16.

Type species. Atelecrinus sulcatus AH Clark, 1912.

Other included species. Adelatelecrinus vallatus new species .

Etymology. From the Greek adelos, meaning obscure, unknown, unseen, and the generic name Atelecrinus .

Remarks. Some specimens of species in this genus are externally indistinguishable from Atelecrinus in having a close suture between centrodorsal and basal ring (Figures 4, 6, 7a, c, 8). However, most exhibit a narrow interradial gap or slit between the centrodorsal and basals (Figure 7 b) not found in Atelecrinus . Adelatelecrinus shares with Paratelecrinus (described below) distinctive deep interradial pits in the centrodorsal rim (Figure 7 d), which separate both from Atelecrinus . However, Adelatelecrinus lacks the complex articular facet on the aboral surface of the basal ossicles characteristic of Paratelecrinus (Compare figures 3d and 7e).