Fig. 17. Oral and ambulacral plating of the callocystitid Lipsanocystis traversensis Ehlers and Leighley, 1922 (UMMP 33311), Middle Devonian, Michigan, USA, illustrating the alternative "B–E the same" pattern of primary brachioles in which all four ambulacra have the first brachiole facet to the left. A1, oral view of showing the four ambulacra and double hydropore; A2, the same with interpretation of oral plates superimposed; A3, interpretation of oral and ambulacral plating. Ambulacrum A stopped developing after the first plate formed. In ambulacra B–E the first brachiole is to the left and the second to the right. B–E, ambulacra; A1a–E1a, first plates in corresponding ambulacra; b second plates in ambulacra B–E; G, gonopore; H, hydropore; M, mouth; P, periproct; 6, 7, orals 6 and 7 under the conventional interpretation. Dashed line outlines of ambulacra and brachiole facets. Only the first two ambulacral plates are shaded.