Comprehensive Description

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General Description

The disk has a diameter between 2 - 3 mm. The disk is flat and covered with small imbricating scales, without ornamentation. The radial shields are distinct with a length twice their breadth. The radial shields are contiguous along most of the length, extending halfway to the centre of the disk. The ventral inter-radial areas have small plates. Well developed arm combs are formed by up to ten small, flattened, peg-like spines, which extend onto the first dorsal arm plate with up to four spines on the plate.

The oral shields are strongly pentagonal and arrow-shaped, with the outer two sides slightly concave. The adoral shields are small, extending to just outside the wings of the oral plate. The jaw is lined by a continuous sharp-edged plate with numerous transverse striations. The second oral tentacle pore opening is just outside the mouth edge with two erect, flattened, pointed tentacle scales. One scale arises from the adoral shield, the other form the oral plate. Two (occasionally three or rarely four) long, sharply-pointed teeth are inside each jaw. The distal portions of the genital slits are partially lined with pointed papillae.

The arms are ca. four times the disk diameter, cylindrical but slightly flattened dorso-ventrally. The dorsal arm plates are oval with the distal edge notched. Most proximal arm plates have four comb papillae. The ventral arm plate has a flat distal edge whilst the proximal edge is pointed. The lateral plates are wide and meet at the mid-line on the dorsal and ventral side of the arm, separating both the ventral and dorsal arm plates. In larger individuals the ventral part of the lateral arm plates is often rugose, particularly on the distal part of the arm as a result of increased growth in the plate stereom. The tentacle pores open with two (decreasing to one distally) flattened, pointed tentacle scales. There are three (rarely four) equal-length arm spines that are less than one arm segment in length. The arm spines are conical, proximally giving way to curved, hooked spines distally.

(Tyler et al., 1995)


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