C. Special Designations for the Species Furnishing Tekhelet and Argaman Respectively.
A baraitha quoted Menahot 44a and the ברייתא בציצית gives a description of the hillazon producing the Tekhelet dye.
As the object of that baraitha is evidently to furnish a clue to the identification of the hillazon, would it not have been sufficient to have simply indicated its special name? Are we to infer then that no such particular designation existed? Or was its special name “hillazon shel Tekhelet” חלזון של תכלת which of course would not by itself afford the key to the identification of the species?
Generally speaking the majority of references to the hillazon have in view of the species furnishing Tekhelet and Argaman, but no one, let us hope, will repeat the initial error committed by G.E. Leiner of huddling up all references to the hillazon as applying exclusively to the Tekhelet–hillazon (חלזון של תכלת).
A baraitha is quoted (75 ,שבתa.) relating to the number of transgressions committed in fishing and crushing a hillazon on a Sabbath day. The Gemara (ib.), in answering a certain question raised with regard to that baraitha, makes a certain statement which can only apply to purple-giving molluscs without supplying the apparently necessary premise that the baraitha must be understood as having reference to those species only. This might be taken as an indication that when nothing is said to the contrary, hillazon in the Talmud should be understood as applying to the purple-giving molluscs. On a closer examination, however, it becomes clear that no such inference is warranted by the passage in question. The tacit assumption underlying the Gemara is simply based upon the self evident consideration that a Jew would have no business to fish any but purple-giving molluscs; for the mollusca belong to the division of impure animals which may not be eaten by Jews: The law also forbids the direct engaging in the commerce of impure edibles.1 To meet the possible objection that a Jew fishing on Sabbath might as well eat forbidden food, I should add that the baraitha deals with transgression due to ignorance (שוגג). Fishing of mollusca for medical purposes would be too rare to necessitate and express negation on the part of the Gemara. Apart from this consideration it is probably that Jews would not themselves fish the species they needed for pharamaceutic uses but would procure them from gentile dealers.