Where the original diagnosis is without illustrations or is accompanied by figues based on two or more specimens, the first subsequent author is at liberty to select from these cotypes a type for the old species, adhering, as far as can be ascertained to the intention of the original author. Such a type speciment is to be designated as a lectotype...
Source: wiktionary
The lectotype and paratype, which are before me, are both iron-stained, predominantly internal composite molds of left valves in a fine-grained, white quartzite matrix.
Source: wiktionary
Lectotype designation is justified under article 74.1.1 of the ICZN (1999) in order to fix the status of this specimen as the sole name-bearing type of this species.
Source: wiktionary