Chaetognatha of the genus Eukrohnia Von Ritter-Záhony in the material of the Snellius Expedition

In 1875 K. Möbius described a new species of Chaetognatha under the name Sagitta hamata. Hertwig (1880) used the name Spadella hamata for it; Strodtmann (1892) called it Krohnia hamata and finally Von RitterZáhony (1909c) gave it the name Eukrohnia hamata. In this "Research" material Fowler (1905) found a few specimens of E. hamata which did not entirely agree with all the characters of Möbius's species; he regarded these specimens a separate variety, which he indicated as Krohnia hamata Möbius var. Von Ritter-Záhony (1909c) gave the name Eukrohnia fowleri to this form. In the material collected by the "Siboga" Expedition Fowler (1906) found only what he thought to be Krohnia hamata. He stated that none of the specimens was actually well preserved, but that as far as could be ascertained there was no reason to doubt their specific identity with Möbius's species. Von Ritter-Zahony (1911c) concluded from the high number of seizing jaws, that Fowler had probably made an incorrect identification and upon re-examination of Fowler's specimens found, besides a few specimens of the true E. hamata, mainly E. fowleri to be present, though in a very poor condition. As mentioned before (Schilp, 1941, p. 39) the material collected by the Snellius Expedition contains 28 specimens of Eukrohnia hamata and 31 of E. fowleri. There are three specimens which I then ascribed with some doubt to E. fowleri, but which on further examination show to belong most probably to the species E. richardi Germain & Joubin, 1916. Only a few of the 59 specimens of Eukrohnia collected by the Snellius Expedition are well preserved, and even in some of those a thorough investigation is made difficult by their opacity.