Orithopsis Carter, 1872: 530.
Type species. Necrocarcinus tricarinatus Bell, 1863, by monotypy (= Orithopsis bonneyi Carter, 1872).
Species included. Orithopsis angelica (Fraaije, 2002) (Fig. 22G), O. carinata (Feldmann, Tshudy & Thomson, 1993), O. ? iserica (Fritsch in Fritsch & Kafka, 1887), O. ? youngi (Bishop, 1983c), O. siouxensis (Feldmann, Awotua & Welshenbaugh, 1976), O. ? transiens (Fritsch in Fritsch & Kafka, 1887), and O. tricarinata (Bell, 1863).
Remarks. Schweitzer et al. (2010: 82) listed only O. bonneyi and O. tricarinatus [sic] for Orithopsis. The synonymy of these two taxa had previously been, however, discussed at length by Wright & Collins (1972), Collins (2003) and Guinot et al. (2008); our examination of the types of both taxa substantiates that view. Larghi (2004: 530) stated that Orithopsis was one of the genera most similar to Corazzatocarcinus and separated them by the ‘marked hexagonal outline and distinct epibranchial lobes’ of Orithopsis. Reduction of both P4 and P 5 in Corazzatocarcinus sets it apart from Orithopsis and excludes it from Orithopsidae.