Cyclaspis thomsoni Calman 1907

Diagnosis. Female. Carapace covered with shallow pits, with a rugose appearance rather than smooth, with single incomplete vertical ridge posteriorly; about 0.5 times as high as long; eyelobe with lenses; antennal notch present; anteroventral corner acute. Pereonite 1 visible laterally. Pereonite 2 not produced dorsally as tooth, but with dorsal keel; pereonites 3–5 with lateral keels. Uropod peduncles longer than pleonite 6; endopod shorter than exopod; endopod with 4 setae medially; exopod with plumose setae medially. Male. Carapace less arched than in female, vertical ridge faint; eyelobe extending beyond terminal margin of pseudorostral lobes. Pereonite 1 not visible. Uropod peduncles longer than pleonite 6, with many plumose setae medially; endopod medial margin with plumose setae proximally and short stout setae distally.

Remarks. In the New Zealand fauna, the most similar species is C. levis . Cyclaspis thomsoni has larger pitting in the carapace, giving a rugose appearance to the carapace, unlike the fine pitting and overall smooth appearance of the carapace in C. levis . Also, C. thomsoni has a vertical ridge posteriorly on the carapace, and there is no such ridge in C. levis . The adult males are the most likely to be confused, as the vertical ridge in C. thomsoni is weaker, and the carapace a little less rugose than in the female.