Bacva Spring, near Pican Village in Istria (in the extreme north-west of Yugoslavia) is noted both for the large number of fossil echinoids and number of species to be found there. They can be collected directly from the stratum in which they occur. Many loose specimens may also be found mixed with scree material.
In this paper an account is given of the lithological composition of the fossil-bearing stratum; position in which the echinoid fauna occurs in the rock, i.e. the position in relation to the bedding plane, interrelation of fossils and their random orientation; range of size of fossils found; degree and kind of damage observed and palaeoecological characteristics of the echinoids and accompanying fauna.
Judging by their ecological characters the genera Conoclypeus and Echinolampas were found in situ. The massive test, the enlarged solid base and the reduced jaw system in Conoclypeus suggest a habitat of turbulent water and gravelly substrate.
The representatives of other genera e.g. Cylaster, Linthia and Macropneustes among others, having thinner-walled tests, well-developed labrum and ambulacra occurring in funnel-shaped depressions suggest a habitat of deeper water with a silty-clay substrate.
That these two ecologically different groups of echinoids occur together is accounted for by a secondary concentration of the fauna due to redeposition by sediment flow.