Original Description: H. W. Parker in 'Annals and Magazine of Natural History' Vol. 11, 1940; "Undescribed anatomical structures and new species of reptiles and amphibians" (257-274).
Key to Central and West African species of the genus Thrasops:
Fewer than 188 ventrals –> 3
2. 13 or 15 dorsal scale rows –>T. flavigularis
17 to 21 dorsal scale rows –>T. jacksonii
3. Dorsal scales keeled –>T. occidentalis
Dorsal scales smooth –> 4
4. 13 dorsal scale rows; cloacal scale single –>T. batesii
15 to 19 dorsal scale rows; cloacal scale divided –>T. aethiopissa (Chippaux, 2012)
Thrasops occidentalis Species Characteristics:
"Ventrals: 175-187
Dorsal Scale Rows: 15-21 rows at midbody, the vertebral row widened
Sub-Caudal: 119-140
*3 labials in contact with lowest postocular." (Parker, 1940)
Appearance: "Rostral subquadrangular, a little broader than deep, visible from above; nasal divided; internasals as long as the prefrontals ; frontal slightly longer than broad, longer than its distance from the rostral (in adult), longer than its distance from the end of snout (in young), slightly shorter than the parietals; no enlarged occipitals; loreal present; preocular 1, separated from the frontal; eye large, its diameter much greater than its distance from the mouth; postoculars 3, lowest in contact with 3 upper labials; temporals 1 + 1; upper labials 8, rarely 7, the fourth and fifth entering the orbit; 4 lower labials in contact with the anterior sublinguals, which are shorter than the posterior. Midbody scales in 15-19 rows, not longer than the ventrals, at least the median rows keeled in adults though all may be smooth in young; ventrals 175-187; anal divided; subcaudals 120-140 pairs." (H.U.M.C., 1863)
Color: "Above, in adults, black; in young, head and neck olive, sides of head whitish, the sutures between the scales picked out in black, dorsum chequered with subrectangular black and yellow spots arranged in 6 to 8 longitudinal rows. Below, in adults, chin and throat straw colored, otherwise dark olive; in young, chin and throat whitish, belly black, the ventrals with alternately two or three transversely oval yellow spots ; subcaudals yellow margined with black." (H.U.M.C., 1863)
Size: "Total length of paratype d 71 (B.M. 66.1.28.6), 1165 (670 + 495) mm. from Sierra Leone; of 9 holotype (B.M. 1911.6.30.2), 1085 (682 + 403) mm. from Axim, Gold Coast." (H.U.M.C., 1863)
