Aclis verrilli Bartsch, 1911

Figs 18E – I

Aclis verrilli Bartsch, 1911: 437, pl. 59, Fig. 6.

Hemiaclis verrilli ― Bartsch 1947: 17, pl. 4, Fig. 5.

Hemiaclis tanneri Bartsch, 1947: 23, pl. 5 Fig. 1.

Type material. Holotype (herein examined): USNM 44811.

Type locality. USA: New Jersey state: off Martha’s Vineyard, USFC sta. 894; 39°53′N, 70°58′W, 668 m; R/ V Fish Hawk col., 02/x/1880 .

Material examined. The holotype and: holotype of Aclis tanneri: USNM 417444 :

USA: New Jersey state: Hudson Canyon, USFC sta. 2234; 39.15 N, 70.0542 W, 1481 m; R/ V Fish Hawk col., 13/ix/1884 .

Remarks. MolluscaBase (2021a) considers Aclis tenuis as the senior synonymy of a group of very similar species described from material of the USFC from New Jersey and Georgia localities: Aclis verrilli Bartsch, 1911, Aclis fernandinae Dall, 1927 and Aclis tanneri Bartsch, 1947 . Such synonymy was proposed by Bouchet & Waren (1983: 306), who also speculated about the possible synonymy with A. walleri; however, the authors were somewhat dubious about the occurrence of A. walleri in West Atlantic and stated that the gap of distribution should be filled for a better comprehension. The occurrence of A. walleri in the western Atlantic (recorded by Verrill, 1880: 391; 1882: 528) was also contested by Bartsch (1911: 438) who considered that the material studied by Verrill (1880, 1882: 377), from the USFC are distinct from A. walleri and he described Aclis verrilli .

In the present study, all types of the above names were examined, and some conclusions could be taken about the validity of them.

Aclis verrilli (Fig. 18E–I) is a valid species and can be distinguished from A. tenuis (Fig. 18A–B) because it has a considerably narrower and multispiral protoconch, besides a faster increase in diameter in the teleoconch. Aclis tanneri (Fig. 18H–I), by the other hand, cannot be distinguished from A. verrilli .

The shell of Aclis tenuis and Aclis verrilli are considerably wider and conical, while A. fernandinae (Fig. 18C–D) has a more cylindrical shape. Sexual dimorphism is known in Eulimidae with females usually bigger than males (Warén 1983), but until we have evidence for this in Aclis we consider both as valid species.