The Echinoid Directory

Palaeobrissus A. Agassiz, 1883, p. 56

[?=Cleistechinus de Loriol, 1882, p. 27, type species Cleistechinus canaverii de Loriol 1882; = Palaeobryssus Meissner, 1903, p. 1343 (nomen vanum) ]

Diagnostic Features	Test ovate without anterior sulcus; depressed in profile. Apical disc with two posterior gonopores and sometimes two smaller anterior gonopores; plating fused according to Mortensen, but basically ethmolytic although madrepores are confined to the anterior part only; positioned anterior of centre. Ambulacra all similar; flush, with hexagonal plates not much smaller than interambulacral plates. Pores in anterior ambulacrum single, those in paired ambulacra double. Subpetaloid. Peristome ovate with weakly projecting labral plate. Plastron plating with T-shaped labrum extending to first ambulacral plate (may just reach second ambulacral plate). Sternal plates triangular; small; fully tuberculate. Episternal plates paired and symmetrical, their suture with sternals V-shaped; tapering strongly to posterior and indented by ambulacral plates 6 and 7 only. Periproct filling most of short posterior truncate face. Subanal fasciole present in juveniles but lost in adults; rounded. Aboral tuberculation of small, uniform tubercles set in a groundmass of granules.
Distribution	Recent, Caribbean.
Name gender	masculine
Type	Palaeobrissus hilgardi A. Agassiz, 1883, p. 56, by original designation.
Species Included	P. hilgardi A. Agassiz, 1883; Recent, Pacific. P. canaverii de Loriol 1882; Miocene, Italy, Cyprus
Classification and/or Status	Spatangoida, Micrasterina, Palaeotropidae.
Remarks	Differs from Palaeotropus in having aboral pore-pairs in the paired ambulacra and biserial ambulacral plating continuing to the apex. Distinguished from Palaeotrema by its double pores in the aboral paired ambulacra. Palaeobrissus also lacks the enlarged primary tubercles bordering the frontal ambulacrum of those two genera. Close to Scrippsechinus, differing primarily in having ambulacra biserial to the apex. The genus Cleistechinus de Loriol, though very poorly known, is possibly a junior synonym. Agassiz, A. 1883. Memoirs of the Museum of Comparative Zoology, Harvard 10 (1), p. 56. Mortensen, T. 1950. A Monograph of the Echinoidea. V. Spatangoida 1. C. A. Reitzel, Copenhagen.