古腹足类的学名，我在北城百科中查到是Vetigastropoda，

那么

For instance,tetrapyrrole pigments such as porphyrins and bilins occur most commonly in vetigastropods and have not been found in the shells of freshwater gastropods (other than someneritids) or land snails [20].

中的vetigastropods应该就是古腹足动物的复数形式。

////2020年2月28日 星期五》》

Conversely,polyenes (mostly thought to be carotenoids) have been identified by Raman Microspectrometry primarily in shells of caenogastropods, hetereobranch gastropods and unionid bivalves [28,29, 31-34].

【相反，多烯（大多数被认为是类胡萝卜素）已通过拉曼显微光谱法鉴定出，主要存在于新生腹足目（caenogastropods），杂支腹足纲和蚌双壳类动物的壳中[28，29，31-34]】

其中hetereobranch gastropods还不知道怎么翻译